You can name up to three teams on the form, but you can only be placed on one team. If you only ship rarepairs, there's a good chance that none of your ship choices will have enough people for a team, but there's a spot on the form where you can default to Team English in the event that happens. :33

English lets you vote and participate in the bonus rounds, but if you want to contribute to your pairings in the main rounds anyway you could consider Alchemiter, where you're allowed to make things for any pairing not represented by a team.