Every year millions of tourists visit Mexico and bring back silver treasures for people back home. Silver is inexpensive in Mexico, relative to other places in the world. You can buy it in galleries, stores, or even on the beach. How do you know you are getting real silver and not getting ripped off?
Look for the 925 mark or 950. This mark denotes the type of silver that you are buying. Sterling silver is 92.5% silver and pure silver is 95.0%. Looking for these marks will help you determine which type you are buying. If the piece doesn't have either of these stamps, it's not real.
Look for a MEX or MEXICO stamp. The second type of stamp you need to look for is one that says either "mex" or "mexico." While some fakes will have 925 stamped on them, it's far more rare to find the Mexico stamp forged. To do so is very illegal and could get the vendor in a lot of trouble.
Check the price. Real silver isn't dirt cheap. If someone wants to sell you heavy silver jewelry for a couple of bucks, it's probably not real silver. Even street vendors sell real silver close to the prices you would find in a reputable silver shop. When in doubt, shop at a store so you can return if you aren't satisfied.
Check for a hallmark. Some jewelers but a special mark on their pieces. Sometimes this is a symbol or sometimes a combination of numbers and letters. This helps you determine who made the piece you are buying.
Watch out for alpaca. Alpaca is called 'German Silver" and looks a lot like the real thing. If you are getting a great deal on silver jewelry, it could very well be alpaca.