Los Pilones is my kind of Mexican, very laid back, great food and excellent cocktails. And last but not least, you can choose from chicken, beef, vegetarian and shrimp! Funnily enough I have never been to Mexico but my time in San Diego has taught me to love any mexican food that comes with shrimp.
The restaurants are in the city centre (Kerkstraat 63) and in the Jordaan (1ste Anjelierssdwarstraat 6), I can't say which I prefer as they are both nice, the former feels more like a dark mexican bar where you can also eat at the counter, whereas the latter feels more like a restaurant, but with a cheerful and still very relaxed atmosphere.
The margaritas are great but so are the other cocktails, as for food my safe bet is the soft shell taco with shrimp, cheese, peppers and onions. If that just scares you, trust me the beef or chicken options are also delish!
PS: Some say Rosa's Canina is good but my time there was a big disappointment.