Yes, you can wear jeans during the day or if in the Caribbean, jean shorts are fine, I usually pack a few pairs and they are nice to slip on over a bathing suit if I need to go get food, etc. Just wear whats comfortable and something thats not too warm if its hot, but yes jeans are fine.
Thanks!..... My first cruise was back in 97', and have been "obsessed" ever since. This will be my 2nd cruise, and I've been reading my brochure cover to cover..... I sailed on RCI's "Viking Serenade", and remember wearing blue jeans in the dining room on casual evenings, as did a lot of people, so I figured black would be acceptable.
If you are cruising carnival, they allow jeans on all nights except Formal night. I was told this directly from carnival. Have been on two carnival cruises, and my husband usually wears nice jeans and a polo shirt to dinner.