MK: For a TS I would take the monorail over to O'hana or Kona (did date night at Kona last February and enjoyed it!). For CS I would go to Columbia Harbour House. ALTHOUGH, if you want to stay in the park, what about The Plaza. It's a cheaper TS because it's sandwiches but it's very reasonably priced, I've heard it's delicious (we're going in February) and they have great desserts (sundaes!).
EPCOT: HMMM, this is the one that gets tricky. There are so many options but a lot of them can get pricey. For TS I would try Les Chefs de France or Teppan Edo (FUN! We're going in February). For CS, without a doubt I would do Sunshine Seasons! YUM!
AK: I would head over to Boma, but if you want to stay I would do Tusker House.
HS: Without a doubt I would do Sci-Fi! We loved it last year, it was so fun! But stick with burgers and fries and you can't go wrong. The shakes are really yummy too! We actually found it fairly reasonable for a TS restaurant, we only spent a little more there then we did at Sunshine Seasons the day before, plus you get to sit in the cars!
DD: For a fun experience I would do T-Rex. We loved it! It's expensive, but the portions are HUMONGOUS! So things are really very easily shared with some still leftover! Or make a meal from the appetizers, I suggest the Triasic Tuna and something else! WOW! That was good!
Resort: For a more romantic meal that won't break the bank like a signature restaurant, what about The Wave at the Contemporary, or again I suggest Kona (Tuna Oscar!).