Southwest Tourism Expansion Act This bill directs the Department of Homeland Security (DHS) to waive the requirement to issue arrival-departure cards to certain Mexican nationals. Specifically, the waiver shall apply to a Mexican national who is (1) eligible for nonimmigrant admission into the United States, (2) exempt from visa and passport requirements or certain existing (and generally more limited) arrival-departure card requirements, and (3) admitted at a port of entry in Arizona on the U.S.-Mexico border for visiting Arizona for up to 30 days. The waiver program shall be in effect for five years. Before the program expires, DHS shall report to Congress on issues including (1) the estimated economic impact of the program, and (2) the number of Mexican nationals who overstayed their visa in Arizona during the first four years in which the program was in effect.