Are you wanting to do the distance in any race, or do you want an Ironman branded race? Personally, I recommend the branded races. Nothing wrong with smaller, local, and cheaper races - but its kinda like this: the smaller races are like the county fair. Ironman branded races are like Disney World. You still have fun at the fair, but it isn't Disney World. Of course, it costs more at Disney World, there are more people, and everything is bigger.
For the first timer I would have always said IM Florida - it was my first one - and I say that only because its flat (which doesn't equate to easy), its more comfortable weather, its a wet-suit swim, etc. Now, after doing Louisville, I would highly recommend it as a first. Yes, its hot and a fairly difficult course, but if you can race smart, have a plan, and be strong enough to stick to that plan, you'll do fine. There is a 15-20% DNF rate at Louisville which is crazy high, but I'd venture to say that 90% of those people didn't have a smart plan or either had one and didn't stick to it.
Florida is hard to get into and if you aren't registered within the first 10 minutes of it going online, then you'll miss out. Most all the IM races sell out within minutes of going online. Louisville does not sell out until a few months before the race - which means you have time to decide if you wanna do it and not have to commit a year ahead of time. People are scared of Louisville and thats why its slow to sell out.
Both Louisville and Florida are affordable (relatively). The hotels do not mark the rates up and require a 7 night paid stay. Most other venues do this.
Florida is Panama City Beach. Great area and great weather. Great race, lots of packs and drafting on the bike - which sucks, but nothing you can do about it except stay away from it. Everything is flat, but the bike does have some small rollers. A flat course does not mean easy. In many ways it can be harder cause you stay so constant. The bike is pretty boring. The swim is in the ocean, and its a mass start - it can be choppy and you'll need a wet suit. Preferably a full sleeve wetsuit. You will be stung by jellyfish - probably several times - probably face and hands. Nothing major though. The run is pancake flat and has lots of spectators - the best spectator group is a group of strippers dressed in their work attire who cheer you on and spank you as you run by. Doing Florida again in November.
Louisville is Louisville...and I fell in love with the city. Awesome venue. Tough course and hot as Hades. The swim is in the river and it is the only Ironman event without a mass start - it is partly against the current and then with the current - but its a small current and doesn't really help or hurt. Bike course - Its a hard but fair course which prevents drafting for the most part, and you stay active while biking with switching gears and having to think - your mind stays occupied and the time goes faster. Beautiful countryside ride. Some pretty good hills but mostly constant rolling hills. Roughly 5000+ feet of climbing. The town of LaGrange has hundreds of spectators lining the streets cheering you on and you go through it twice - very cool. the biggest climbs have spectators wearing devils suits, costumes, etc. much like you see on the Tour de France. Nice to see. The run is flat for the most part - good spectator support. Some good groups here, too. One little girl who was maybe 6 years old was on the side of the road, and as everyone passed her, she would say "don't worry, I pee'd in my pants too". Anyway, good supported race. The finish line is crazy good. The Louisville volunteers were amazing. Can't say enough about them. Will do louisville again. I told Kristi I would take a year off from Ironman, but I am really wanting to do louisville again next year - so maybe next year.
If you want a nice wintertime vacation, then I'd say do Cozumel. If Louisville is in my top 2 favorite races, the other one is Coz. This is actually a really affordable trip too...you'd be surprised i bet.
Anyway, thats my take on recommendations. I did Coeur d'Alene a few years ago, but the cost of that trip will keep me from doing it again. Great race though. There are a lot of smaller iron distance races that are great (B2B) and worth considering.
One more thing that I forgot to mention. Only in an IM branded event do you get to hear this - and it never gets old hearing it:
Keep all laughs and snickering to a minimum please.
I really enjoyed Cozumel. If you don't need the security of a wetsuit it is fine. The bike is a little windy but wasn't too bad when I did it. The entire island is out supporting the race. The race essentially takes over the island.