I'm a beginner skier and looking for a place to practice telemark turns. More specifically, a very gentle slope with a nice runout, preferrably in SG (but SB or SJ is okay), where I don't have to worry about mowing anyone down on weekends. Since I use waxless Nordic skis, and need workout anyways, I can ski up (say upto 300 feet in elev at a time) and yo-yo all day long.

I checked out Baldy service road from Manker, but it now has a packed, pock-marked rut running down its length due to hikers (even above the Hut trail cutoff) and is too narrow due to snow build up. Have heard nice things about Waterman area, but nothing specific. I do have a high clearance 4X4 with two pairs of link chains, as well as skins for my skis.

Thanks in advance for any suggestions.

I'm also a telly beginner. Spent last year doing day-hike/runs on Mt. Winston, just across the road from Mt Waterman Ski area. I've not been up this year. I think that is a part of the closed area due to the burn. It's a real fun beginner hill. Takes about 40 minutes to skin up to the top and you can get a nice run on mellow trees and meadows.

Mt Pinos has lots of space and easy ground. I've not skiied up there yet. Long drive.

Definitely places up at Mt. Pinos, skiing from either direction from the parking lot up top, assuming the road's been plowed that far.

If not, last winter I tooled around on XC skis up near Charlton Flats and found a couple decent, open slopes, that's assuming ACH is open. Just across the road is Mt. Mooney, which is pretty gently angled and may have some open areas to practice.

I'd probably be up there myself but my skis are up at a cabin the So. Sierras.

Until I started making laps on chairs lifts I never got anywhere with telemarking.

It's all about mileage.

I just skied Cuyamaca Peak in San Diego Co this morning....and yes, the fire road is destroyed from post-holing boots and tennis shoes all the way to the top but there is room to roam off the road every so often.
You won't find anything in SoCal that you can just drive up to without dealing with boot prints thanks to easy access. The Dry Lake approach to Gorgonio/Charlton has big wide open slopes to play on.....I just haven't gotten up there yet.....still "training" with my new set-up.

I second the Mt. Pinos suggestion. Also, skiing the 2 (ACH) from either side of the traditional winter road closures at Islip Saddle or Vincent Gap is a lot of fun on skinnies. Not sure about current access on the HWY, however.