I'd love it if prostitution became legal and regulated. It probably would lower rates some, but it would also probably lower the cost of doing business as well. Part of why our screening process is so thorough is that, unfortunately, if someone does get violent, it's harder for us to involve law enforcement. Generally we have some sort of private security, but it's not the same. Legalisation would also make it much easier to crack down on truly exploitative agencies (and pimps, and human trafficking) because as it is now, we're all under the same umbrella. There's a world of difference between someone like me and my coworkers and someone who has been illegally brought to this country to serve as a sex slave, or someone whose pimp forces her to have sex for his profit.
I get tested for STDs pretty much constantly anyway, so it's not like that would be different. As for keeping it a secret: I'd happily come out to everyone who knows me, as awful as that would be, if it helped prevent slavery and rape.