There's a chance you won't be able to ride any rides that have a height requirement, but there aren't that many of these; most rides you will be able to go on with no problem. Here are the rides which do have height requirements-
In Disneyland:
Matterhorn & Gagets Go-Coaster = 35 inches (it's possible he may reach these by February)
All the "mountains" (space, splash & big thunder), also Star Tours = 40 inches
Indiana Jones = 46 inches
Note that the Disneyland site lists Autotopia as having a height requiement, but this is the requirement to be able to drive. Your son can go with you as a passenger, since he will be over 1 year old when you go.
In California Adventure:
Tuck and Roll's Drive'Em Buggies (bumper cars) = 36 inches
Jumping Jellyfish, Soarin', Tower of Terror = 40 inches
Grizzly River Run, Mullholland Madness = 42 inches
Note that the Disneyland site lists Redwood Creek Challange trail as having a height requirement, but this is only for the zip-line; definitely go here and play around- this one's a toddler must-do!
California Screamin' and Orange Stinger = 48 inches
Maliboomer = 52 inches
I confirmed these with the Disneyland website
http://disneyland.disney.go.com/disneyland/en_US/help/gsDetail?name=HeightRequirementsGSDetailPage (the lower ones I know by heart from trips with my 3 & 5 year old sons; the taller ones I had to look up).
So really this is a pretty short list, and if you do want to go on some of the height-requirement rides, you and your husband can take turns by doing a "baby-swap". Basically if you go to the cast member checking the heights for the ride and show them that you have a child that's too small to go on the ride, they will give you a pass that allows the second parent to go through the fastpass line (the first parent either needs a fastpass, or has to wait through the normal line).
Have a great time planning your trip!