Legal Question in Business Law in California

If the contractor is truly "impossible" to schedule, or even nearly impossible, that's a breach, but I'd start by reviewing the signed quote carefully. Does it say anything about what constitutes a breach, scheduling of the work, or the like, and if so, how does it bear on the situation? If there's nothing in the signed quote (i.e., the contract) that points in another direction, you might write him a certified letter giving him a reasonable time to schedule (say, 14 days) and a reasonable time to complete the work. State that if the work isn't scheduled to your mutual satisfaction before the 14 days (or whatever's reasonable) expires, you'll consider him in breach and the signed quote void and unenforceable.