The tap water is safe to drink. Do not flush toilet paper. Credit cards are universally accepted, but you may want some cash for tipping for things like housekeeping, avoiding an automatic 10.0% tip at coffee shops, etc. The immigration lines are bad. Expect to wait about two hours after your flight unfortunately. Sorry, y'all!
An ATM is the best way to get money if you are getting $150 USD or more. Bank ATMs should charge low fees or no fees. Your bank may charge a bit – maybe $5 per transaction and 3.0% on the money withdrawn, if that. However, the exchange rate will be pretty darn in line with the true exchange rate. If you are getting a lesser amount of money, your hotel may be a good option. Just check the rate that they are offering against the actual rate. Avoid exchanging money at the airport. Also, exchanging money before leaving may be a poor choice. The rates tend to be poor in both instances.
Use Ubers to get around. While they are technically illegal, a passenger will not get in trouble for using Uber. When riding in an Uber, the driver may ask one of you to sit in front. Do not be alarmed. This is only so it looks less like they are operating an Uber.
Restaurants: typically 10.0%. Most bills will have a voluntary 10.0% tipping charge. You do not need to pay it, but everyone does. Bars & cafés: round to the next significant amount. Cafés and bars may add a 10.0% automatic tip when you pay with a card. Housekeeping: $1-$2 USD per day. Ideally, pay the equivalent in COP, since the locals would prefer the local currency. Taxis: not customary. You can round up. Hotel bags: $2,000-$5,000 COP total.
Naan Laureles: This is an Indian restaurant with great garlic naan and chicken tikka masala. There is also a good local microbrew list. Restaurante Idilico: This place has great Colombian food. The Raw Wahoo was epic if it is still on the menu. Don Diablo Steakhouse Medellin: This spot has excellent steaks and great food all around. The steak tartare is crazy good and unique. Also, the cocktail game is on point. Alambique: The atmosphere is cute with a bunch of antiques and greenery. While the cocktails are good, they definitely tend to the sweeter side of the palate. Hija Mia Coffee Manila: This is a coffee shop with a good americano.
Fear not! 30 5mg tablets of finasteride is less than $7.00 USD. You're welcome.