You'll have time to learn the solos, and improvising them for now is a good approach. When first rehearsing a song as a band, you have to get the groove down and then get the song form down. It's unlikely that you'll get both of those down in one rehearsal session. Even if each individual has it down on their own, it still takes time to get it down as a band, especially if you are just starting to play together.

Have fun and don't expect miracles at the first rehearsal.