Are cars useful for travel in Montevideo?  Riding in someone else’s car is definitely a help for getting around the city, but renting a car of one’s own is strongly recommended against.

Taxis are an excellent means of getting around Montevideo ( http://www.tripadvisor.com/Travel-g29... ).   They are somewhat more expensive than the other public transportation in the city, which is made up of a network of buses.  Despite this, they are relatively inexpensive and are good for use throughout the city, especially at night, when the safety of walking through the city center decreases and the buses stop running.  Travelers will find that the taxis are safe and that drivers generally speak enough English to facilitate communication.  Taxis are metered but travelers should discuss rates with drivers before accepting rides just to make sure that everyone is under the same impression about what the ride will cost.

Another option to get around is the "Remise" it´s like a taxi but more confortable and profesional. Remise  don´t use a protective glass  between front and back seat like the taxi, units are full equiped, taxi don´t have aircondition,  because they have protective glass .
Rates: you can find different rates because they don´t use meter , but must common is rent by hour  and it's around U$S 18 per hour with 15 kilometer free, if you exceed these 15 kilometers free,  you have to pay around  U$S 1.20 per kilometer.  Remise also it's used also to make a transfer from or to airport and you can find rates from U$S 37 to U$S 55. The most  used are: Airport Transfer Montevideo , Taxis del Aeropuerto,  etc. 

In contrast to the ease of using taxi service in Montevideo, rental cars are both expensive and difficult to use.  The streets of Montevideo, especially within the downtown center of the city, are compact and crowded and visitors will find that car travel is not easy.  Additionally, rates on rental cars are considered prohibitively expensive, particularly in comparison with the low cost of other modes of getting around the city.

Drivers in Montevideo are quite good and if you can drive in any metropolitan city, you will be fine here.  The rules of driving are very loose, but when an intersection has no stop signs or lights, you just slow down and look.  You may like that better than the U.S. system where you have to stop even if nothing is coming.  It is easier to drive here than Buenos Aires, which is a whole other story.  Think "bump-em cars"  with only getting as close as you can without the bump.