Can I mail in China visa application, photo, and passport, or must I use a travel agent or agent do it?

In Chinese consulate in Houston, NO visa application can be done through mail, email, internet, or any express delivery service such as UPS, FedEx, etc. Visa application should be submitted and picked up by the applicant or someone else entrusted.

What if you dont live anywhere near? Say florida?

If you live in florida, you also need to submit the application to the China consulate general in Huston.