(PM reply sent--please check your In Box, CODiver78.)
(Thanks, PhilPug--"check's in the mail") 
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Hi CoDiver78--and welcome to EpicSki. While I can't agree with Phil that anything I might say "might as well have come down on tablets from the heavens above," I'll offer you a few thoughts, some of which have already been raised by others above.
First, although I do not know your athletic background other than that you skied once a long time ago, it is likely that you are not, actually, a complete beginner. It's amazing how much tends to stay with you over the years after you've been on skis even just a little. One of the hardest things for most beginners is simply the unfamiliarity of the sensations of slipping around on long feet. But you've done it, and I'll bet you find that you retain more of the experience than you expect.
For this reason, I don't recommend that you take your first lesson in a big group of beginners. You've identified most of my reasons yourself--large, impersonal class, more-often-than-not led by a very inexperienced instructor, unfortunately. And beginner classes, especially when the instructor lacks experience, tend to proceed at the pace of the slowest student. With your prior experience, minimal though it may be, I doubt that you'll be that person!
Private lessons are very expensive, as you know. But they offer the personal feedback and pacing you want, and more importantly, you can request a particular instructor. In any ski school these days, the staff will range from very part-time "hobby" instructors with little or no experience and training, to full-time, certified pros who have dedicated their talents and careers to the profession. It's like comparing a first-grade student to a PhD. The problem is that in most group lessons, especially at the lower levels, you'll have no choice--but you'll probably NOT get one of the top pros.
On the other hand, group lessons can be worthwhile and productive experiences. If the group is well-matched and not overly large, and the instructor is a good one, you can have a great time.
Here are some suggestions.
- For your first lesson, take a private half- or full-day lesson, if you can afford it. (Locally, Copper Mountain may offer the best prices, since they reduced their private lesson rates substantially last season.) If you have an instructor in mind, request him or her when you sign up. If not, request that you ski with no less than a current PSIA Full-Certified (Level 3) instructor. Ask around--and inquire here at EpicSki--for instructor recommendations at any resort you plan to ski.
- After that first lesson, you may get great results, and have a great time, with a few group lessons. The multi-lesson packages you've mentioned at Keystone and Breckenridge should be good. Of course, you will still do well with more private lessons, but I do understand that the cost can be prohibitive.
- Although as one of its coaches and founding director I am surely biased, I cannot recommend highly enough our own EpicSki Academy. There are two in Colorado this season--first at Arapahoe Basin for three days, December 3-5 (Friday-Sunday), and then at Aspen-Snowmass in January. The cost is considerably less than private lessons, and the coaches are the truly elite--trainers and mentors of other instructors from across the country. Groups are small--generally six or less. I strongly encourage you to come to the Arapahoe Basin event, at least. It's early in the season, so it will get you off to a great start, building the fundamentals that you'll continue to develop throughout the winter. It would be fine to start out at the ESA, but if you could get in a day or two on snow first, especially with a half- or full-day private lesson, you might get even more out of it (particularly if you take that private with one of the ESA coaches). You can learn more about EpicSki Academy here. I won't go further with this, lest it sound too much like a commercial, but I cordially invite you to the EpicSki Academy.
Regarding your other thought about "underground instructors" from Craigslist or elsewhere, I don't recommend them. As others have noted, for starters, they are completely illegal. It's a long story, and frankly, I'd love to see the legal environment change to allow private instruction and competition, but the way it is now, it cannot be done without breaking the law. More important (perhaps), the instructors who do it are rarely worth skiing with. Rarely do they have any real training as instructors (instructor training comes largely from ski schools themselves and from PSIA, which requires employment at a ski school for certification). Indeed, the only way they can succeed at all is to fly under the radar. Any reputable instructor would be quickly recognized, kicked off the mountain, and probably arrested. For substandard instruction (especially at the early "formative" stages), it's just not worth it!
So, please join us at an EpicSki Academy, and best of luck with your goals. I think you'll have a great season, and I'll bet that you'll go well beyond your objective to ski blue runs (comfortably) from the top of the mountain (although I'd never promise that you won't fall--falls are part of learning and skiing, at any level!). Please keep in touch, and don't hesitate to ask any questions and to share your experiences with the rest of the EpicSki community so we may all benefit.
Have fun!
Best regards,
Bob Barnes