there are 2 alternative restaurants, sabitini's (italian) and the desert rose (tex-mex) and also the horizon court, which puts out a nice dinner spread. you basically dress however you want in these places. my wife and i were on golden in march, and loved it.
have a great time.
If you choose to go to Sabattini's or the Desert Rose you do have to abide by the dress code of the night. Therefore, if it is formal night, you must dress formally. This is not the case for Horizon Court. This would certainly be an option for you if you choose. We ate at the Horizon Court on French night ( not big on frog legs or escargo) and it was very good. Your other option would be to do room service. You can either ask your room steward for a copy of the dinner menu or view the menus posted outside of the dining rooms at any time during the day. As long as you know what's for dinner they should be able to bring this to your room.
I hope that you will reconsider your decision to sit out the formal nights, as these are the nights when special events happen -- things like the Captain's "welcome aboard" reception and the champagne waterfall. It's also fun to see everybody dressed up so nicely. Formal attire is expected for all of the entertainment as well as for dinner, so you won't have many options if you refuse to dress for the occasion.
To answer your questions, though, yes, you can order anything on the dining room menu through room service during dining room hours.
I have never seen anything from Princess saying that formal attire is optional on the Horizon Court on formal nights, though a lot of folks seem to have the impression that it is. The Horizon Court offers a dinner buffet in the early part of the evening and a bistro for late dining.