Is it the RER - B that we take. Does anyone know how much it is and if it is safe. Should I buy passes before going to Paris. Thanks.
It's safe. Just from memory I think it's something like 8.50 Euro and you buy the tickets from a vending machine. Absolutely no need (or, I think ability,) to buy from the States.
Yes, it's the RER B. That's the only line that goes to CDG. So long as you use common sense and keep an eye on your luggage in crowded areas, the RER and Metro are perfectly safe. The fare is 8.20€ (includes transfers to the Metro and/or other RER lines so long as you don't exit the system). Keep your ticket. You'll need to insert it in a turnstile if you exit at a RER station. (Not necessary if you exit at a Metro station.)
The ticket machines won't accept credit cards that don't have an embedded chip. Go to a window if you want to use a credit card.
Also keep your ticket becuase there are inspectors on board that will soemtimes check to make sure you have your ticket.
Last weekend I was picking up my friends from CDG and one of them didn't hear me say "hold on to your ticket"..the inspector came around and she had thrown hers out, ouch.