Hi jl039,
I’m happy to help with “how” to choose but there are far too many unknowns and variables for anyone to help with specifically “what” to choose out of all the thousands of mattresses that are available in the market (see post #2 here)
The first place to start your research is post #1 here which has all the basic information, steps, and guidelines that can help you make the best possible choices … and avoid the worst ones.
When you get to step 3 … then some of the better options and possibilities I’m aware of in the Los Angeles area are listed in post #2 here.
Phoenix
PS: Just to let you know … the forum software system is sending you notices for replies to this thread which you have subscribed to and the email notifications are bouncing back with an explanation that they are being blocked as “unsolicited” or “likely spam” by your email service.