I'll tell you what I know (not much
) and I hope it is of some help.
Spring Valley Lake is not a gated community like Canyon so people are free to drive in; however, it does not tend to get alot of outside traffic. The lake has several fingers where the speed is limited, and a main body of water where you can ride/ski/drive faster (just like Canyon). The main body of water does not appear to be as big as Canyon Lake's (I have had an airborne view of both lakes).
The riding is likely to be simular to Canyon lake. You can probably forget about glass in the summertime (except for early mornings or a lucky weekday) because it wouldn't take more than 2 or 3 boats to tear it up. On the flip side, it is probably pretty good this time of year.