From Yuma, a day trip to Los Algodones is a must. Compared to other places I've been in Mexico, Costa Rica, Beijing, and Bankok, it is a haven, clean and friendly. The vendors talk politely in English addressing you as "sir" or "amigo," and if you say, "No, thank you," they immediately stop.
The main attraction is dental work--inexpensive, fast, and high quality. The money pouring into that town must be astounding. There were thousands of people, all going to the dentist or buying pharmasuticals (saw a lot of people carrying big bottles of booze too). We didn't buy anything, but had a good lunch in a sidewalk cafe--fish tacos $1.50.
The best part is the RV park is literally right outside the door, about a 100 yard walk across the border. The park is called Sleepy Hollow and is owned by the Quechan Indian Tribe.