Here's a whole day plan in Palermo:
1. Morning
Japanese Garden, JardinJapones.org.ar., Casares 3450 in Palermo. Authentic Japanese garden experience. Enjoy an hour or more strolling the grounds. There's a Japanese restaurant with lunch for US$5 to $10. Food is OK for the price. Sake is on the menu, but didn't try it.
2. Check out some of the special cafes around town:
https://www.laguiadebuenosaires.com/cafes-de-especialidad-en-buenos-aires/
3. Late afternoon meal or dinner:
An alternative to premium-priced Don Julio, is "La Payuca" at Arenales 3443, near the Alto Palermo mall. Open noon to late night. Lunch set menu (small steak, fries, drink) from noon to 4pm, less than USD$10. I prefer the bigger steaks on the regular menu, which go for about half the price of Don Julio. We ordered 300g steaks from the regular menu, and with a glass of house wine, less than $30 for two. Excellent. For parents, they offer a kids play floor upstairs.
4. Dessert
Next door to Don Julio, the famous steak restaurant, is possibly the best made-from-scratch cake cafe in town, "Kajue Cafe" at Guatemala 4665, Palermo Soho. Specializing in several varieties of cheesecake, carrot cake and others. The young owner went to cake school in Colombia, and speaks good English. Friendly staff.
5. Bar:
Don't miss the Alcatraz prison-themed speakeasy bar, "The Hole", in Palermo Soho, at Armenia 1743, half a block from Costa Rica, open until 3am. Even has a vintage car from Prohibition era, and fake guns. Sushi is on the menu. It can be hard to get in on the weekend, as a long que forms even before they open at 8pm, so a weekday night may be best.