Once you get in Rey it is possible to find the interesting places by foot. But since there is no map in Lonely Planet guidebook and the distances between major objects are rather big, it is wise to take a taxi unless you are on a very tight budget. There is a taxi stand right outside the metro station. Take the taxi for about 2 hours to visit all places you are interested in and bargain hard for the price.
Rey can easily be reached by metro(red line). Once in Rey, I walked around and found it to be completely fine.