One of the most famous street? Media Luna.

Ok my friend, if you are a very easy going person, traveling without an expensive plan, well you must go to media Luna Street, in this place you can find cheap and clean hostals and you'll be in the center to the city (Getsemany)  the most special places to stay? Hostal Mamallena/ Hostel Media Luna
They have a very bigs parties, you just have to be carefully with some local persons selling drougs, there you'll never know "who" is the person that is selling you  and "what" are you buying.

Then you have Plaza Trinidad very near of Media Luna street, this is my personal pre-party place. I used to buy some beers and drink with my friends there hihihi.