I have read several posts about whether or not Carnival is a "party", "drunk & punk" cruise line. Well. I am 39. Have been both single and divorced and have been on singles, couples & family cruises. 19 cruises in total (from the lower-end Carnival to the 5 star Cunard & Crystal lines).
My response to the Carnival comments is "you are all correct". It depends on your itinerary/length of cruise and the time of year that you are traveling. If you are planning on going on Carnival on their shorter 3/4 day and even the 5 day cruises....you will be on a ship with many party-goers, singles, groups & families looking for value (and many first-time cruisers) Now, if you are planning a trip during to the Bahamas/Mexico during "Spring Break" then you will likely get a boat loaded with people looking to party (now if this is not for you...consider booking in the winter months....even Thanksgiving or Christmas (some good deals to be had around these holidays). Summer is usually a pretty dead time for the cruise lines and you can get some good deals (consider avoid 4th of July, etc. if you want to avoid the heavy partying). The Alaska cruises tend to have a tamer and classier crowd too.
Now. No offense to Carnival....but they are the Kmart/Walmart of the cruise lines. They work on high-volume & low price. They are strictly value oriented. You will not be pampered. The shows are fair. The food is fair. The Carnival kids programs were very bad and two of their day-care worker were pretty horrible. The cabins and the decor are not that great. Their private island is average. The atmosphere & nightlife are definitely geared toward fun. However....to many....the price is right. I didn't find Carnival very roamntic at all. Carnival would be a good choice for a group trip...ie a reunion, a bunch of friends/teachers getting together...singles...and families (it is a pretty good value if you have never crusied before). My 4th (and last) Carnival cruise ship caught on fire the day after we got off. I won't be going back for more.
However, if you are looking for something a little classier....a bit tamer (but not lame) and something romantic....then consider Celebrity Cruises. It was very close to 5-star quality at a 3 1/2 star price. A very, very good value (more expensive than Carnival but less expensive than the true 5-star lines). I've been on 8 cruises with Celebrity and have loved every one of them (Alaska was breath-taking). The rooms were large for a cruise ship and the food was superior to almost every cruise line that I have ever been on. Celebrity is owned by RC....but RC hasn't changed Celebrity's winning formula. RC (Royal Caribbean isn't bad either....I just don't find it to have the same price/value ratio that Celebrity enjoys). Cunard & Crystal are 5-star lines....they were nice....but my were they ever snooty. If you want pomp....and papal pampering (and a heft price) then these 5-6 star lines are for you. The crows are much older....same with Holland America (but Holland America is more of a 4-5 star line).
Do yourself a favor....evaluate the time of year you are travelling....where you are planning to travel too and the anticipated length of your trip.
I've also generally found that the shorter the cruise...the less relaxing it will likely be for you (anyone who has cruised knows how long & painful dembarkation can be..and a 2 day cruise...followed by dembarkation just doesn't cut it). 3 days is ok. 4 & 5 days is better....more time to relax. I personally found 7 days pretty much perfect for my tastes...although I would like to do a 10-21 day sometime.
Hope this helps. No matter where you go....and no matter what line you choose.....HAVE FUN and BON VOYAGE!!!!!!!!!!!