Most attractions will have good availability. The "headliners" for each park (FOP, SDD, SDMT) will probably not be available at 30 days, but just about everything else will be.
The thing to remember is that there's really only one super-hard to get FP at each park. So if you're willing to be strategic (get there early for RD, get into line right before closing, try to 'refresh' your way into same day FPs), you can still ride what you want without a FP. The other thing to remember is that even if you end up doing a long wait for that one attraction, it's just ONE attraction. If you have FP for the other things, you can plan for that one long queue to be snack time, game on your phone time, watch a video time, etc.
Also, remember that FP availability is becomes more fluid closer to your dates. Just because something isn't available at 30 days doesn't mean it won't be available at 7 days (people cancelling room-only reservations) or the night before/morning of because plans changed.