Dinner in the specialty restaurants is enjoyable time to relax enjoy your food. If you do not want to take a chance and meet someone you don't care for than only sit by yourself. After having good times meeting other people on the cruise over the 5 times we have been on the Rivera or the Marina, sometimes you hit a bad apple, so just make sure you stay away from them, if asked to sit with them say you would prefer not to and mention it to the person who seats you so they do not end up at your table, just be nice.