Before even travelling to Bariloche you need to have a proper bike to do the trip. There are several options. One being renting a bike in Bariloche and paying an extra fee to return it in San Martin, or bringing it back yourself by bus.
According to my research that was more than double the price of bringing it down with me, for that there are also two options.
1- Flying it with you, for which you need to procure a bike box, taxi it to and from the airport.
2- Shipping it by bus and avoid all the airport hussle.I took the second option shipping it 3 blocks from where I live in Buenos Aires. the company name is "Via Cargo" and they have offices all over Argentina.