Safety really depends on where you go in Mexico & it's getting more dangerous -- Americans are targeted, especially solo. You're safer in the big resort areas, but that kind of vacation has never appealed much to us.
You can just get a passport card for Mexico & Canada, but I'd get the full passport since it is good for 10 years. You won't need a passport for Puerto Rico or the Virgin Islands, & these are nice alternatives.
The passport card is only good for land or sea travel, not air travel. Get the full passport book.
Puerto Rico is nice, fun, inexpensive, and has the protections of being an American territory. Though it definitely feels almost as foreign as Mexico, and there are safety issues in San Juan. It's like a 3.5 hour flight from the NYC area, so it's going to be closer than Hawaii.
I've been to Mexico between 10-15 times, both to border areas (Matamoros, Reynosa, Juarez, Tijuana), tourist areas (Cancun, Puerto Vallarta, Nayarit), big cities (DF, Monterrey), and non-tourist rural areas (San Luis Potosi state, etc.). If you have a reasonable head on your shoulders, Mexico is no more dangerous than visiting New York, Washington, or Philadelphia. Especially if you're looking at Tulum, Playa del Carmen, etc. Don't vacation in Michoacán or Guerrero. Stick to the well-trod tourist paths as a travel newbie. Learn a few Spanish phrases. You'll be fine and will have a lot of fun. Mexico is dirt cheap right now with the strong dollar.
Also, Hawaii is great, but super expensive. Others have spoken about that already.