Notta. There are as many vendors on 5th Ave trying to support their families as there are sharks trying to be a hassle. Learn to say no and avoid eye contact with the sharks is easy enough. When they ask "where you from?" just say Russia. They will just wave you on and you can go about your business. The vendors between Juarez and the Ferry Terminal are worse than say the vendors between Juarez and Calle 16. There is a great variety of souvenirs and best prices at a shop on the beach side between Calle 2 y Calle 4. They take pesos, USD, Euros, whatever. I got 6 t-shirts for 6 dollars USD; shot glasses for a buck. Do not try shopping on your last day early in the morning. No one opens up until after 8 or 9 and you will find yourself shopping at the airport for souvenirs. That's much more of a tourist trap than Quinta Avenida.