Groceries:

All the markets have fresh fruit and vegetables. Generally speaking, prices go up as you get closer to the center. So the Terminal Minerva market is the cheapest, followed by La Democracia, Las Flores, and the Centro Comercial by the park. You can get most everything else you need at these markets as well (particularly in La Democracia and at Minerva) but if you feel the need for a true supermarket experience there is always Despensa Familiar or Paiz. Other interesting natural foods (granola, etc.) are available at Al Natur (#10).

Used Clothing:

The Minerva market has a big section full of used clothes from the USA. You can find amazing deals here. Bargain away, but look particularly for the 3Q piles. Also check out the many clothing stores scattered around the city.

New Clothing:

La Democracia market has lots of nice clothing — Guatemalan-made in the street stalls and more expensive imported stuff in the shops.

Electronics:

There are many electronics shops along 12th Avenida (“La Doce”), but you can also find decent deals in the shop right on Parque Central. If you’re looking for something for an apartment check out La Pulguita along the side of the cemetery near Parque El Calvario.

Alcohol:

El Rosario on 8th Calle (D12-21) near Mercado Las Flores has good prices, but if you can’t make it there you’ll be okay in any tienda.

Souvenirs:

Parque Central on the first Sunday of each month is best, but also look in the Centro Comercial next to the park or inside of the central market in La Democracia.

Gear:

La Aventura in Mont Blanc (”paiz” in the microbuses).

Musical Instruments:

La Panamericana on Parque Central.