Both DC and Philly have very active TER boards. Look over to the left at Regional Boards and hit the arrow to find them and many others.
Cant speak for Philly but DC guys will be happy to give some guidance if you can give us a hint as to the type of girl your looking for.
DC has lots of touring girls as well so you will like the choices ..not to mention the costs which in general are lower than Vegas.
As to screening, use TER and go from there. If there are no reviews definitely move on. EROS relibility is about like Vegas. Very iffy and most be verified elsewhere. Backpage, Cityvibe have about the same level of reliability and Craigs List is ..well you probably know already...
Hope this gets you started. Best wishes to you!