We stayed at the Valencia Travel Village last year for a week. It is in a handy location for a lot of stuff. It is a very old park with some really tight spots on the west side and kind of noisy if you are near the highway. Office staff was great.
I looked at Malibu Beach RV Park. It looks awesome but there is review after review about how terrible the staff is etc.
DW and I have been there twice and the staff was great. We would go back again. But like someone else mentioned, it can be a two hour drive from MM. We have not stayed at Travel Village nor Lake Piru (didn't know about that one).