Hi divebrasil - I stopped in Cabo last May on my way home to PDC to visit some friends and get a couple of dives in. I hadn't been there since the mid-90's, and boy, had it grown. I find Cabo San Lucas to be VERY Americanized - when I spoke Spanish to a taxi driver, he looked at me like I was an alien and answered me in fairly impeccable English.
It isn't a large city like Cancun, with high rise after high rise, but it does have some large hotels in the core area. The remainder are kind of like the Mayan Riviera hotel stretch - big resorts sprinkled along the highway connecting San Jose del Cabo and Cabo San Lucas.
Yes, Cabo is chock full of American chains. But you don't have to eat there. There are many many other good choices.
Personally, I prefer Playa del Carmen (I live here), but I do enjoy visiting the Pacific side on occasion. The scenery is beautiful, particularly the rugged Pacific coast. If you drive from Cabo up towards Todos Santos (home of the infamous Hotel California of Eagles fame), there are some stunningly beautiful spots to stop at. The combination of desert and hills and ocean is very different from the flat jungly tropical Yucatan.
The diving I did was good - colder than here, different critters, Sea Lion pups that were just a joy to see, and a Manta sighting. For me, nothing beats the cenotes, though!
If you are interested, here is the website of a friend of mine, fellow Canadian transplant to Mexico (MexiCanuck!). He has lived in Cabo for years, and basically knows everyone and everything.
Caboguy.com - Get Connected in Cabo San Lucas !