They sent out invites last Friday. The interview date is Feb. 19th. If they have another interview date, they will probably have more invites go out later, but i doubt they will send out more invites for the Feb. 19th interview (not that my opinion means anything, but that wouldn't give much time for them to organize the logistics). I think UCSD really depends on the professors to give names of students to interview. Have you been in contact with any professors?