Santa Fe isn't exactly a huge backpacking destination so don't worry about huge crowds or reservations. In summer, around the end of January, there is the Fiesta de la Cerveza (beer festival), and in winter, in the middle of April, the Fiesta del Alfajor Santafesino, which is all about eating delicious sweet cakes and other treats. Summer is hot, but there is access to river beaches if you need to cool off.
Here are some related tips to help plan your trip to Santa Fe: Safety,
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