Define "Spring." If you're starting in February:
Feb 7 - Huntington Beach, CA
Feb 13 - Mesa, AZ
Feb 14 - Austin, TX
Feb 14 - El Paso, TX
Mar 7 - Napa, CA
Mar 21 - Los Angeles, CA
Apr 25 - Eugene, OR
May 2 - Vancouver, BC
As far as I know, all of the above are still currently live races. I doubt LA will be run live due to its massive size. I have run Mesa, Eugene, and Austin and can give them all a "thumbs up".
Mesa is very fast and we had great weather, not many fans but a solid field. It started getting warm later but the under-3:00 group had good temps through the end.
Austin has some pretty good hills, especially in the first 3 miles and again around mile 9 I think. Weather can be too warm for a fast time. Very well organized race.
Eugene had I believe two small hills that I barely noticed and is a fast course. Very well organized and good crowd support (as one would expect from "Tracktown"). We had great weather with a little rain that actually felt good. Finish with a half lap around Hayward Field, tough to beat.