Getting to San Felipe from America is easier than you might think. Take your passport with you and shouldnt have any problems crossing the border either way. Make sure you NEVER bring drugs or guns to Mexico. Even if its a shark gun or a bang stick that you keep on your boat, leave it in America. They are not lenient with firearms of any kind nor drugs.
This second map is a reworked map courtesy of Alan Smith, Sacramento. I took it from the San Felipe Mexico websitethat is a valuable resource. The people that take care of that site do an amazing jog. Here is the link http://www.sanfelipe.com.mx/index.html
The next map was taken from the amazing San Felipe MX site. It is broader map all the way down to Puertecitos.