It's probably all less than $2000, so disposing of it (i.e. throwing it away) is probably ok, though I'd want to make sure that the place is actually abandoned first (i.e. post eviction notice and wait 14 days to make sure they haven't come back or something, not sure exactly what would be correct here, might want to confirm with a lawyer).
Selling the stuff gets complicated.. and I don't know how throwing the bike away in such a way that it happens to land in your garage counts.
Tenants suck eh?