My partner and I (late 30's early 40's) have always sailed on RCCL in the fall (less families with children) and have never had a problem with anyone. Even our dinner companions have always been warm and welcoming to us. Of course we don't walk around holding hands to make it obvious, but we are together all of the time and people have always been kind and have even asked us how long we have been together (I guess they figured it out without us telling them)
We always choose a balcony because it's soooo much nicer to open up the doors and hear the ocean and feel the breeze with a drink. I think it's worth the extra money involved, it enhances your cruise experience. I won't go on any cruise less than 7 days because we enjoy them so much and anything less would be disappointing to us. We actually don't like to get off after the 7 days are over. We have only sailed on the Voyager class ships and you hardly even feel the ocean even when it's rough out with the stabilizers that they have.
Enjoy and don't worry, you'll have a fantastic time!