Philadelphia is based on a grid system.  North-south streets are numbered, beginning with Front Street (which used to be 1st Street) at the Delaware River and continuing west across the Schuylkill River to 69th Street.  Broad Street is the main north-south street.  It would be 14th Street if it was numbered, so 2nd to 13th Streets are east of Broad Street and 15th to 69th Streets are west of Broad Street.

East-west streets are named.  Most east-west streets in Center City have tree names (Walnut, Spruce, Chestnut, Pine, etc.).  The main east-west street is Market Street.  If a street address has north in it (for example, 500 N. 22nd Street), this means the address is north of Market Street. and, alternatively, streets with south in the address are south of Market Street.  City Hall is at the junction of Broad and Market Streets.

Taxis can be hailed anywhere.  Uber and Lyft also operate in Philadelphia.  Public transportation is bountiful and is operated by the Southeastern Pennsylvania Transportation Authority/SEPTA (http://www.septa.org/).  You can ride the Philly Phlash (https://www.phlvisitorcenter.com/ride-philly-phlash%C2%AE/) for US$5.00/day.  It loops around the historic district, museums, and cultural areas.  The closest stop to the DoubleTree Hotel is at 12th and Market Streets.