Hotels and hostels:
Staying in Rio may be a bit expensive, I’m afraid, even taking the exchange rate in account (roughly 3:1 for Dollar and 4:1 for Euro). Even so, try booking a hotel somewhat near PUC-Rio, not only for convenience sake, but because you’ll be closer to a tourist area, in neighborhoods that are safer for wandering at night.
I don’t believe there are any hotels in Gávea, the small neighborhood in which PUC-Rio is located, maybe a hostel, but you should try finding a suitable hotel in Leblon or Ipanema, or even Copacabana or Botafogo. Read the “subway” section and use Booking.com to try to locate hotels or hostels at walking distance from some subway station (see Getting to the venue section).
There’s an Ibis hotel near Cardeal Arcoverde subway station and another one near Cantagalo subway station, both in Copacabana. There’s also an Ibis hotel near Botafogo subway station, which is also an excellent option for it’s convenience. Maybe they are good suggestions, since they tend to be less expensive.
But don’t trust my opinion, search Booking.com for better options, just try to stay in one of the neighborhoods I’ve mentioned above.