I live up here, so I'll do the best I can to answer your questions....
The beach is about an hour away. You go down the 15 to the 76 and it dumps you out at Oceanside pier area. Nice beach.
As far as the drive... I have to go to regular monthly doctor appointments in La Jolla. If I leave my house at 7:30-8:00 it takes me about an hour and ten if there are no accidents. If you are leaving to be at work at 6, you will run into much less traffic, but it's still a drive. The construction in Escondido is what slows the drive down. When that's finished I'm sure it will be much better. The 5pm dirve is about an hour and ten. If you have a good sound system in your Civic and are not anxious, you are good.
The Temecula area is a lot like Orange County now. Nice new neighborhoods, stores of every kind, etc... The houses are big, new, and cheap. The properties are usually pretty decent sized too.
Murrieta is more of a ranch community, with several housing tracts stuck in it. There is only one hotel in town, and not many big restaraunts, but tons of small ones. If you are looking for a big chain store or restaraunt you drive the extra mile to Temecula. The cities touch each other.
Tons of businesses of every kind here. Murrieta is more of a rural feel except for the area up against Temecula.
The weather here is very different than SD. It's sunny all the time here, and can get hot during the late summer. But that's what swimming pools are for. I still don't have the top on my Jeep and will probably have to put the soft top on soon because of the rainy season. But the sunny days most of the year make it nice for my mesh top.
I lived in Orange County for many years, and got tired of the foggy days constantly. Not to mention the traffic, but if you live in SD you are used to that.
Off roading pretty much doesn't exist here except in the riverbed and areas a little further north by Lake Elsinore or south like Lawrence Welk.
They are not as bad as SD as far as pulling you over for not having a front license plate or lifted vehicles. If you don't drive like an idiot they pretty much leave you alone.
Your decision is about the commute. If you don't mind the extra time in the car, you can get twice the house here for a lot less money. People in the grocery store will strike up a conversation with you, everybody is pretty friendly for the most part here.
There are LOTS of Jeeps here too, and they wave.
We love it here but are spoiled by the area we live in and have a five acre ranch on the outskirts of town. It's super quiet and gets dark at night. But the freeway and stores are only five minutes away.
You have some thinking to do. Spend some time up here and see how it feels.
Hope that helped.
Betcha' wish your girlfriend was as dirty as my Jeep!
Zombies hate fast food.
Hang on! This is gunna' be a thrill ride of geriatric proportion!