Open 6 days a week (closed on Saturdays), La Trailita (it's a food truck, but before their current truck, they were just a small trailer) serves some of the best tacos and quesadillas in Chicago, including tons of vegetarian options. They are open year round (even when it gets cold!). There is another taco truck across the street at the intersection, so make sure you're going to the right one (it's in front of a convenience store). I believe it's run by some ladies from the church it parks near. Recommend their tacos al pastor and potato quesadillas. Salsa is very tasty but very spicy!
The South Gardens at the AIC are magical––go in the middle of the summer when the whole gardens are lush, the flower pots are overflowing, and the leaves have came in on all the trees to form a sun-dappled canopy. Make sure to look at the Fountain of the Great Lakes––each woman in it personifies one of the Great Lakes of the region, and when the water is turned on, their seashell basins flow into one another in the same direction of the real lakes.
The best new/used bookstore in Chicago––and with every sale, they put money towards buying books for classrooms in the neighborhood schools. Great selection, well organized, helpful staff, and they hold occasional events where they'll stay open late.