The weather is cool, partly rainy and actually pleasant. Is Fountain Valley in north or south California? If you are accustomed to really warm weather you will need a sweater/warm jacket + a raincoat or umbrella. It can get quite cool in some parts of the country, especially Jerusalem. Locals are still wearing their heavy winter coats!
If you like nature, plants and birds it is the ideal time of year. It might not be best on some days for long city walks but the rains are beginning to end, so you will have sunny days too.
I checked the site that Chris sent - it is pretty accurate as far as it goes, but March is very different than April. It is still closer to our winter than our summer, which actually often begins in April. We have no Spring to speak of.
Welcome and feel free to write me for more details.
Debbie - Israel