http://www.employees.org/~calridng/allsites.html#anchor1035169 is alink with a map of most of California's riding areas. Miami is USFS #44 on the map. I've never ridden an area near Sequoia Lake, so can't help you there. I think some of the USFS areas on the map that are southeast of Fresno are well removed from main routes, so they would still take a long time from LA, even though they are further south than Fresno. Miami is just off a main route, so access is easy.
I never had a good trail map of the Miami area when I was up there, so I am not sure how much total trail mileage there is. The maps I had were incomplete and hard to follow, and lots of the trails were not well marked or unmarked. I might have a trail map scanned in on my home computer, but won't be able to access it until this evening.
Exploring around I was able to find a few good ones - the trail that runs parallel to Hwy 41 from the Tillamook (sp?) staging area is OK, and links up with a few others. I also remember a trail called MMTE or something like that which was pretty good and fairly long.
I think there is probably enough to keep you entertained for a few days if you are not too picky and don't mind riding the good stuff more than once. Its not big like Stonyford, but If you have a dual sport, there would be some good fireroads to check out.
Have fun! My inlaws have a place up at Bass Lake, but were are not heading up there this holiday so there is no chance to join you.