Well, technically in Foxborough, as that is where Gillette Stadium is. No word yet on when tickets go on sale. Plan is to put a natural grass on top of the synthetic turf. For any of you who can attend, this would be a great chance to possibly see some of Villarreal's players in action for the Spanish national team, and Jozy Altidore will certainly be part of the US squad.
Often post-season friendlies are an opportunity for a coach to look at some players who haven't seen much time (Bruno, Borja possibly?) but given that the last time these two clubs met the US defeated Spain in the Confederations Cup, Spain is going to want to bring a pretty strong squad I would think. For the USA it's their last game before the CONCACAF Gold Cup, with a game on June 7.
Ticket information will be forthcoming soon I expect. More information as we learn it.