No, gays should not be allowed to adopt.
At it's very core, adoption should be about finding the best home for foster kids. That means finding a home with a good, positive male role model and a good, positive female role model. Single adults shouldn't be adopting because that's not the best home. Gay partners shouldn't be adopting because that's not the best home.
Society should fight for unalienable rights for every person until they affect someone else. In the case of adoption, you shouldn't jeopardise a child's chance of a good upbringing just so you don't hurt gay people's feelings.