Mazatlan is hot in May. My first mistake was bringing my rollerblades. The Golden Zone is not rollerblade friendly and it was too hot to blade anyway. My second mistake was renting a bicycle. At 300 pesos a day (about $20, the exchange rate was just over 15 pesos per dollar), it was more expensive than round trip taxi (by Pulmonia, those white golf cart look-alike things) from the Golden Zone to old town. Furthermore, I was sore from biking and walking every day, which necessitated many massages (everything is pretty cheap compared to DC). However, if you really want a multi-day bike rental, then Baikas will deliver a bike, helmet and lock to you in exchange for rental fee in cash and your driver's license as collateral. Now let's talk about food.
I was staying at El Cid El Moro beach, on top of Señor Frog (there's only 1 Señor Frog restaurant but many "official" stores selling froggy merchandize). I did not choose all-inclusive, otherwise this would be a pretty short post. I did have lunch there on arrival at La Concha (the indoor/outdoor restaurant overlooking the beach), dried chicken Caesar salad and slightly fishy ceviche, so it's not just my bias against resort food that leads me to say the food there isn't worth writing about.
On that first evening, I went to Pancho's, a Lonely Planet recommended restaurant on the beach a short walk away. I had a pretty chewy shrimp taco followed by a Mexican Plate of quesadilla, taquitos, tostada, chile relleno, and a piece of grilled meat. Other than its scenic location, you probably couldn't distinguish this place from your local Tex-Mex restaurant, which is to say it's filling, cheap, and nothing special.