Exporting to Mexico

I am currently doing the research to export to Mexico. There are some key steps to follow to ship items at a reasonable cost. The best way to send merchandise (so far according to my research) is by using the USPS and filling out the customs forms. Would the items arrive to Mexico and safe? how long would the shipment take to arrive? Well...I'll be trying that out within the next 2 weeks....and we'll go from there. If everything works well, I'll start listing items in Mercado Libre in sets of 2 so the final customer saves on the total shipping cost. (I calculate that to be between $ 16 and $20 USD per shipment - if under 4 lbs). We'll see what happens from there.