I agree with Fatboy ^ on the Negra Modelo. Dos Equis amber's great too. Those are my two choices at a Mexican restaurant. If they have neither, something's seriously out-of-whack.
I'm sure lots of people have great micro-breweries in their area these days. I do too - Gordon Biersch. Their Marzen is a smooth, rich amber lager - highly recommended! It's about all I've had since the first day I tried it. And if you're ever in Palo Alto or San Jose, you can visit the brew-pub/restaurant.
Btw, Trader Joe's resells it under their label, calling it Vienna, at least that's the rumor (GB does brew beer for TJ's - that's a fact), so if you have a TJ's close to you ...
http://www.gordonbiersch.com/brewery/beer/index.html