Okay I can help you because I had this experience as a west coast cruiser. I think all new cruiser make this mistake. You aren't certain if you will like the cruise so you book a short 4 day cruise. The problem is
the stops on the 4 day where Enseneda and Catalina. Enseneda isn't even worth getting off the ship. Also this cruise has quite a bit of the younger college aged crowd.
The stops on the 8 day are Acapulco, Mexico ; Zihuatanejo/Ixtapa, Mexico ; Manzanillo, Mexico. There is a huge difference between these ports and the ones on a 4 day. Also if it's a longer cruise when the kids are in school you will have a complete different type of cruise passenger. Less college kids on spring break and more older couples on vacation.
To resolve the cabin issue i agree with the other posters, you need a balcony room of some kind. If you can open a door and be outside you will feel better. So it you can get one with an extended balcony I think these are in CAT 9A check with your Travel agent. If after the eight day cruise you don't love it then cruising may not be for you. It isn't for everyone. I just think the 8 day will give you more of a true impression on why we enjoy cruising.
On a personal note my first cruise was the same 4 day in 1994 and I didn't cruise again until 2003 that was on a 7 day and boy what a difference.
I have cruised every year since.