You may want to consider The Renaissance in Long Beach. Plenty of interesting activities and place nearby!
Likewise, if you go to San Diego, The Marriott Marina is a wonderful hotel and plenty to see and do nearby as well!
Good luck and welcome to MRI! Hope you will have more questions and share your travel experiences with all of us!
If San Diego is a good choice I highly recommend the Marriott Resort on Coronado Island. Beautiful location, tons of flamingos. You have good places you can walk to and a great view of the bridge and downtown.
Up in LA I highly recommend the JW Marriott Le Merigot. Definitely one of the most pampered Marriott experiences I have ever had. I didn't want to leave the hotel. Santa Monica Hotels Near the Beach | JW Marriott Santa Monica Le Merigot