'bout time we had some nice weather.
Any biking is good to get in shape. A 50 mile road ride is good for the endurance; mountain biking can be good interval work out - but of course nothing beats time on the track.
Find your rythem and speed for the track and know when you want to go beyond it (for a sprint) and what your steady pace feels like.
For elite nights, there is a fast and a slow group. If you can do 20mph in a pace line for 40 laps, you should be ok (you can always drop). That is probably about the same as 15mph solo for 10 miles.