SAN DIEGO — San Diego may finally get long-awaited rules this spring for sidewalk pushcart vendors, a growing part of the local economy that faced a possible ban from some business districts and tourist areas in 2019. San Diego Mayor Todd Gloria plans to revive regulations that were abandoned midstream by his predecessor, Mayor Kevin Faulconer, after backlash from advocates for minorities and low-income residents. Supporters of new regulations say a city crackdown is needed to fight chaotic and dangerous conditions created by vendors who illegally dump trash, don’t handle food hygienically and block access to restrooms, emergency lanes or mass transit.