MariaElena,
In downtown Cabo, do not miss the Nowhere Bar. It really is a great place for dinner (especially if you like sushi) and mostly for grabbing a few coctails & hanging out. It's more "adult" than some of the more well known spots, it sits right on the marina and has wonderful service. That's my big PSA.
Also if you are into eating a lot of food, try Brasil in downtown also. They do something like a 10 or 12 course meal for $25 (last time I was there). It's kinda cool, they bring these big swords with different kinds of meat to the table & slice it right onto your plate. There is no way you can eat everything they offer you! It's just a fun place.
Also, there are so many cool little spots that I can't remember the name of, but I'm sure you will find your own by just exploring.