Plot: Ruth and Bettina take a road trip to Mexico, leaving the men of Fisher & Diaz to some male bonding--and comic-book crime-fighting. David and Keith open up after closing their 'open' relationship; Claire warms up to Jimmy after getting the cold shoulder from Edie and Anita; Billy resurfaces as a substitute art teacher; and Nate can't decide what he wants from Brenda, who turns to old friends to treat the pain