SAN ANTONIO (AP) — San Antonio Mayor Julian Castro is joking that he won't emulate Clint Eastwood at the upcoming Democratic National Convention.

City residents gave Castro a sendoff Saturday before he heads to Charlotte and the DNC, where he'll give the keynote speech. The San Antonio Express-News reports ( ) that Castro signed autographs and posed for pictures inside a crowded auditorium.

Castro told the crowd he'll speak about San Antonio, which he said looks like "the United States of tomorrow."

Castro also joked about Eastwood's speech Thursday at the Republican National Convention. Eastwood, the Oscar-winning director of "Million Dollar Baby" and "Unforgiven," brought an empty chair onstage and imagined President Barack Obama was sitting in it.

Castro says, "I won't lie to you, I won't be talking to any empty chairs up there."