Ooooooooooooo. Lots of options here.
First off, someone will undoubtedly hijack this non-skiing related thread to point out that Loveland and A Basin will be open in Colorado (or did I just do that?)
1. Bellingham to La Jolla - I don't know those roads well enough to suggest very much. I don't think you have very many road options, so you'll likely just be traveling down the coast down I-5 and maybe jumping onto highway 1 for the interesting bits.
2. Whew.. I thought I could help on the next stretch because I've spent a lot of time in AZ and NM. But you're way south since you're in San Diego AND you have at least 1700 miles in front of you. I'm guessing you're planning on leaving the same day as the wedding, so it shouldn't be too bad. You're far enough south that you're going to miss the great parts of AZ and NM - no worries - you have plenty of time to pick some of them up on the return. I would:
a) Oct 5th - if you don't mind leaving as soon as the wedding is over, jump right in the car and start driving - I-8 to I-10 and end up in Las Cruces, NM for the night. It's a long stretch - drive fast. Your fallback plan would be to just drive to Tucson and then spend time late in the evening going to Saguaro Nat'l Park.
b) Oct 6th - From Las Cruces, head up to Albuquerque. This is a very long detour, but head up to the Balloon Festival! You'll likely miss the balloon events on the 6th since there's not too many. That's ok, it'll give you a chance to find the grounds where it's at. Wake up VERY early next morning to see Dawn Patrol, watch the morning competition, and then head out on the road.
c) Oct 7th From Albuquerque south through Roswell - not much to see here, but get a silly bumper sticker and alien paraphenalia to prove you were there. Then drive down to Carlsbad - tour that. Head towards San Antonio and try to get as close as you can (you probably won't make it the whole way.)
d) Oct 8th - You like music, you should check out what shows are in Austin and San Antonio at that time. Those cities have some of the best music scenes in the country.
e) Oct 9th - Drive from there to Lafayette.
3. Coming back.. alright, this is where you can have some fun.
a) You're that close to New Orleans, you have to go there on principle. Spend at least a day doing that.
b) Now your goal is to get to Cimarron, NM as fast as you can. There is nothing else worthwhile seeing on the way. Houston and Dallas are sprawling examples of the worst of urban planning and soul-sucking pits of suburbia. Oklahoma should be auctioned off to highest bidder. Going further north into Kansas is simply an act of desperation and entirely unnecessary. Instead, just drive fast. One possible exception - you can get a 72oz steak at the Big Texan in Amarillo. It's worth the stop.
c) In Cimarron, stay the St. James hotel. Something like 22 men were hauled out of there feet first back in the 1800's and the bullet holes in the ceiling are still there. Drive south out of town and admire the huge Boy Scout camp.
d) From Cimarron, drive US-64 across to Taos. Stay in Taos. Eat at Michael's Kitchen (not actually the best place in town, but close, and you can't go wrong with a single thing on the menu)
e) From Taos you're going to head through Colorado, I'm just going to recommend one circuitous route. You didn't mention if you like to hike at all, so I'm not going to recommend hikes (unless you want me to.)
f) We'll skip Santa Fe... but it's a cool city.
g) North from Taos through Alamosa and spend the night in Durango. Possible stop at Pagosa Springs for soaking or the Sand Dunes to admire the oddity of sand dunes in CO. If you go to the sand dunes, drive out the west entrance and stop at the alligator farm in that area.
h) North from Durango to Silverton - spend some time admiring this little town - head outside of town to see the ghost town of Animas Forks.
i) Will you have 4WD? If so, head over Cinnamon Pass (not Engineer Pass!!) to Lake City with your destination for the night being Gunnison. If you don't, head up past Ouray. I'd recommend stopping at Orvis Hot Springs - one of the best in the state. Your destination for the night is Montrose.
j) From those locations, drive through the Black Canyon of the Gunnison Nat'l Park. Drive through Paonia and go to Aspen.
k) Leave Aspen. I'm sort of out of ideas here. Optionally you could extend your stay in Colorado by driving through Vail, Summit Co, and Steamboat.
l) There's not a lot to see leaving Aspen and head north through Colorado. You'll want to drive through Rifle and Craig. Possibly tour Dinosaur Nat'l Park.
m) Your destination is Jackson Hole, just drive as fast as you can to get there. Apparently we auctioned the western half of Wyoming off to Exxon and it's a complete wasteland north of Rock Springs. Not that there was much there before. (The hidden gem here is the Wind River range - one of the best and most unknown parts of the Rockies - excellent hiking/backpacking hiding here.)
n) Spend some days doing this: Jackson, Teton Nat'l Park, Yellowstone Nat'l Park. Buy some kind of floating device in Jackson.
o) Do you fly fish? The Madison and Gallatin rivers outside of West Yellowstone are superb playgrounds for anglers.
p) Drive out of Yellowstone via the west entrance (West Yellowstone.) Drive to Ennis, optionally stop in Virginia City - a completely restored town from the 1800's. Everyone's head will turn when you walk into _the_ bar - you're not a local.
q) Drive through Norris, head towards Bozeman. Stop at Warm Springs and get out your floating tube. Jump into the Madison River and float down to Black's Ford - approx 3 - 4 hours. Drive on to Bozeman.
r) From Bozeman you need to head west on I-90 back to Bellingham. Maybe stop in Couer d'Alene on the way back?