My DH and I went to Cabo last May and loved it! We went for both of our 40th birthdays and our anniversary. It was perfect weather every single day and we stayed at the Riu Palace, super nice!
Check into Puerta Vallarta. The city has many different types of lodging options from super-fancy beachfront chain hotels to condos to quaint older hotels and villas beachfront and in the hills.
The old part of the city is nice to walk around, couple of houses of note (Elizabeth Taylor's & Richard Burton's, for example), old churches, etc. And here's a website with sights to see outside the city: http://www.puertovallarta.net/what_to_do/sightseeing.php
We're going to Los Cabos in March and we're staying at Riu Hotel for 8 days. My DH booked it for us as my birthday gift, I'm excited!!!! What else can we do there aside from eating and relaxing.. any recommendations i.e restaurants (love fajitas)...etc.. Thanks!