Is everything really casual down in the keys? I'm kind of assuming it is as I think about what clothes to bring. I'm figuring a few bathing suits, shorts, t-shirts, and maybe a light pair of pants..
Anything more "dressed" for an restaurants or bars? We'll be in Islamorada week of March 20, but will be driving around, definitely to Key West..
Do you think I'd need a light jacket at night?

Shorts, long-sleeved chambray shirts and tennis shoes is my daytime attire. At night, I might slip into a pair of jeans or khakis. there are a few places - Louie's, Seven Fish, A&B Lobster House, & the restaurant at the Marquesa - where some people semi-dressup, some of the time.

In Islamorada, the restaurant at the Cheeca is about the only spot that MAY be semi-dressy.

So, yes, it is a casual place.

I've been to the Keys in every month of the year and I've never worn a jacket. Then again, I'm hot natured. Sometimes, on the water, it can get very windy and a jacket may be called for then.

Bathing suits and sarongs are uniform of choice for most women during the day and into the night.

The dressiest I've ever been in Key West was a sundress over casual flip flops.

Anything involving closed toed shoes (not including tennis shoes) or socks is overdressed.

I don't think I've ever seen anyone in long khakis.

I'm really only familiar with Key West as I've only been to Islamorada once, but you may be assured it's very informal. Having said that, there are restaurants in Key West...Louie's Backyard and Michael's come to mind...when I'm more comfortable in pants rather than shorts and so is my husband. This is NOT to say there aren't others wearing shorts, it's simply our preference. March will probably be very warm, but I usually take a light sweater in case there's a cool breeze off the water.

It is difficult to be "under dressed" in Key West

The average temp. in the Keys in late March is (high) mid 70's, (lows) mid 60's. Not really jacket weather, but if you do get sunburned, that mid 60's in the evenings can feel kind of chilly (at least for this Floridian!).

Everything is casual in the Keys! I once called the Little Palm Island resort (very, very expensive place) to ask their dress code for dinner. I fully expected to hear jacket and tie. I got "shorts must have hems and men's shirts must have collars." In other words, no cut-offs and t-shirts. That being said, you may want to have long pants for dinner. It's just a matter of what you are comfortable in. As to a jacket - yes, bring it. It won't take up much room and you may need it. In Islamorada, be sure to eat at Morada Bay (no long pants required!) If you want samething fancier, Pierre's.

Regardless of what you bring to wear, TAKE BUG SPRAY! I was in Key Largo this weekend and was eaten alive. Have fun!

NYTimes Frugal Traveler has an article about a family going to Miami and Key West, that might be interesting..
I hope it is warm, have fun!!

Unless you plan on going to a really nice dinner pack very casual for Key West. I did bring a suit and tie just because I knew we were going to dinner at A&B Lobster House. Was kind of a hastle but it was for an anniversary dinner.

Thanks for your replies--that makes it much easier to pack! I can't wait to go and leave winter behind. 22 days to go!