I had hit and miss luck with no PS days last Feb. There was a two hour wait at Whispering Canyon, so we ate at the snack bar. But we could have walked into Artist's Point. No luck at Teppenyaki, but the tempura bar was open. No luck at all for lunch in MGM (Sci Fi, Brown Derby, 50s), ate counter. Walked right into Marrakesh (like you usually can).
I'd really recommend making a PS for every other day - just in case. You can always call and cancel it the morning of, and always call ahead and see if you can get booked it - even if its just 2 hours ahead of when you want to eat. Just book it and present it to your husband as "I've made reservations here, let me know if you want me to cancel them the morning of." No PS may doom you to an existence of burgers and chicken fingers (or dinner at Marrakesh or Akershus - both which are wonderful, but if you don't know what you'll be in the mood for, chances are you aren't going to luck into the "mood" for Norweigen). Although Disney does have some great variety in fast food, you have to know where to find it, and be willing to plan ahead a little to get it. Its far too easy to tour until you are starving, and then be unwilling to search out good food, or wait 40 minutes to get it.
Good non-PS Food in the Parks:
Much of Epcot. The cafe in Morrocco, the sandwichs at Norway, the fast food stands in the Land stand out. The tempura bar and lounge in Japan don't take reservations and have decent sushi if you want something different.
We are fond of the sandwiches at Cosmic Rays in the Magic Kingdom. Huge sandwiches and a good value.
Almost all of AK is fast food. Try Tusker House.
MGM: I'll let someone else suggest something, I've yet to have a good meal here.
Generally, hotel resturants are pretty easy to get into - and are among the better restaurants anyway. There are exceptions (like CG during fireworks, or Whispering Canyon.
You don't need to call 3 months out either. You can try calling with a list a day before you leave - your husband may have a better feel for things then. We usually call for all of ours about three weeks out. Chef Mickey's (I've never tried for Cindy's) is hard to get that close to travel, but I generally get everything else I'm looking for, within an hour or so.