I am a food purist (why ruin something that is so pure and delicious even in its most simplest form), so I really really really enjoy a burrito with black beans, rice, and cheese. Yep, that's it. Sometimes though, when I'm feeling a bit adventurous, I'll throw caution to the wind and add a bunch of stuff. This happens rarely. But still, the grilled chicken, boiled chicken, guacamole, different salsas, and vegetable mix are all good.
I would recommend a burrito and a cup of horchata, which is ridiculously cheap and ridiculously delicious (it is homemade). Last time I think the whole meal cost me about $6.
If you're not in San Rafael, Gordo's (yes, this translates to "Fatty's") is somehow familially related to Puentez but they have more locations: three in San Francisco - Clement St., 9th Ave, Geary Blvd. - and three in the East Bay - Telegraph Ave., Solano Ave., College Ave. All of these places are worth the effort and the prices are more or less the same.