The Ottawa airport is not far from downtown and the cab fare is affordable. You can also take the bus from the airport to downtown: it takes 20 minutes and it is very cheap. Ottawa has a very good transport system. The bus will take you anywhere, but all recommended hotels are downtown.
The conference will take place at the Novotel downtown. 33 Nicholas Street Ottawa, Ontario K1N 9M7 613 230-3033.
It may be that you do not find a cheap direct flight to Ottawa, but to Montreal. Once at Montreal Trudeau Airport, you can either take a short flight to Ottawa or the bus (it takes two hours on the bus). The bus will take you downtown in Ottawa, very close to the University and the Novotel, in fact where most of the hotels are. You can also take the train from Montreal to Ottawa. The train station is very close to downtown, the university, and the Novotel. However, note that the bus may be more convenient than the train since the bus leaves directly from the airport, and not from downtown Montreal. Note that the bus must be booked in advance (via the Greyhound website).