Efrain's (the original in Lafayette, though the other locations I've been to are also good) is IMHO, by far, the best Mexican restaurant in Boulder county. It is not without it's faults (merely ok margs and salsa and hit-or-miss service), but the strength of their best dishes coupled with the generous portions and very affordable prices make it a clear winner. Their chile verde burrito is superlative: it makes your face sweat while also being full of flavor. That said, the dish does vary (probably with the cooking staff): some days it's awesome, others, merely quite good. My wife and I also dig their altogether too humble sounding ""beef burrito"" which comes in an absolutely amazing (and fairly mild) red sauce. That said, the portions are generous and the prices surprisingly low.
Efrain's margs are ok. Served in a mason jar with salt (unless you request otherwise) they are generally reasonably priced and unremarkable
The service can be spotty. Sometimes you get lots of attention from your waitperson, other times very little. In my experience, there is little correlation between business and overall level of service.
Overall, I think it the best Mexican restaurant I've tried in Boulder county. It's nothing fancy, but has great food, great value, decent salsa/margs and highly variable service.
Pros: Best Chile Verde in the greater Boulder area
Cons: Quality of service and heat of chile verde burrito varies
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