When the topic of eating lunch in Frisco comes up, usually everyone just scratches their heads wondering what's worth going to. Usually Taco Bell ends up winning.
If you want something on Main St, then here's my suggestions:
1. Po Boys near 5th St. It's downstairs and has a decent lunch menu with beer.
2. Backcountry Brewery. Completely overrated, but with the new ownership things have gotten better. Be careful of the microbrews + altitude combination. Their beer is around 6 - 7%.
3. Moose Jaw. Dark, dingy, and a locals favorite. Just order the burger.
4. Blue Spruce Inn. Sit in the bar and order off the bar menu. It's sort of like and upscale Moose Jaw.
5. A Train. Pizza. Beer. Never been there.
6. Boatyard. When you walk in the front door you'll know in 2 seconds if you want to stay for a drink.
There's better restaurants in every other town in the county, but places listed above aren't that bad.