Montevideo is a compact city, so most places can be reached on foot. However, if you prefer, there are taxis and buses available. Expect to pay around $5-$10 for a taxi ride and $1.50 for a bus fare. Uber is also available in Montevideo, with similar pricing to taxis. Allow travel time of 15-30 minutes between locations.
If you have more time, consider taking a day trip to Colonia del Sacramento, a historic town just across the river from Buenos Aires. If you have less time, skip the natural hot springs and spend more time exploring the city. Be sure to try the famous Uruguayan dish, chivito, a delicious sandwich filled with steak, ham, cheese, and vegetables.