I am going on a four-day breather with my finace to key west. We plan on mainly lounging, but would like to take advantage of the restaurants we've read so much about. Will I need a rental car?

Car isn't really needed. Taxis around town are plentiful (and most things are walking distance). Good restaurants:
Cafe Marquesa and Seven Fish.

If you are staying in an area that they call Old Town you won't need a car but if you are staying in New Town you by all means will.

Most of the really good restaurants are in Old Town so if you are staying in that area you will be able to walk to them or take a very quick taxi ride.

Better without a car. You can rent bicycles and mopeds. If you are staying in the Old Town almost everything is in walking distance.

I guess the big question is which area of the island are you staying on?

THanks for all the replies - we are staying in Old Town at the Wyndham Reach, so it seems like we'll be ok.

You will have a bit of a walk but if worse comes to worse you can always hail a cab. Watch out with the Reach......It is kiddie play land.

ooohhhh, The Reach. That place will nickel and dime you to death! If you don't believe it ask about the "resort fee".

You will have a bit of a walk from the Reach to cover most of Duval/Old Town. Just allow plenty of time and enjoy the scenery and people watching! There are bike rentals and pedicabs in addition to regular taxis. I suggest Blue Heaven On Thomas for dinner/breakfast, Pepe's on Caroline for breakfast, El Siboney on Catherine if you like Cuban, B.O.'s Fish Wagon on Caroline for a sandwich at lunch, P.T.'s for late night snack, Flamingo Crossing on Duval for unbelievable homemade ice cream. If you want upper scale dining, Louie's Backyard has been named Key West's best restaurant many times but is hit and miss. No one locally seems to know why but when they hit boy do they hit! There is a fantastic, tiny bar to the left just as you go in the door. Great quiet spot for a drink. Most of the other bars in Key West will provide anything but quiet! For some fun there is the usual Sloppy Joe's, Hog's Breath, Captain Tony's, Rick's, Durty Harry's, etc. but try the Bull Bar on the first floor, Whistle Bar on the second floor and for a real surprise (clothing optional) the Garden of Eden on top.