The best time to visit Puerto Peñasco is April. Temperatures are up, in the mid 70s, and the weather is generally arid. Prices for accomodation are reasonable low, especially if you avoid Easter week-end, the busiest time of the year here. Expect to pay around $120/night for a hotel room.
If you don’t like rain, avoid July at all cost. While the weather is generally dry in Puerto Peñasco, July is monsoon season with heavy rain and subtropical temperatures. If you’re into bike shows, visit Puerto Peñasco in November, during the Rocky point Bike Rally. This is one of the best bike gathering south of the border.