The Lake District is glorious from spring to autumn, and Bariloche itself is very busy in January and February. Trekking is best from January, as the higher paths may still have snow on them until then, and is generally fine until the end of March. You'll find fewer tourists in March and April.
Note: flight, boat, train and bus timetables change constantly, and airlines come and go, so please do not rely solely on this information for your travel planning. Check with relevant companies, or a flight search engine like Skyscanner, first.
There are several flights a day to Bariloche from Buenos Aires (with a flight time of around 2 hours), and some in summer connecting Bariloche to other towns in Patagonia, including El Calafate and Puerto Madryn (these vary year to year). Try Aerolineas Argentinas and LAN.
There are also frequent long-distance bus services (often overnight) with comfortable reclining seats - see Via Bariloche and Andesmar.
For information on international travel to Buenos Aires, see our guide on getting to Argentina.
From Bariloche, hire a car to access more remote places and to make the most of the landscapes. See our car rental recommendations.
Alternatively, many places can be reached by bus; Via Bariloche connects main towns, and within Bariloche there are frequent buses along the lakeshore to Llao Llao, and up to Cerro Catedral for starting hikes and going skiing. Cyclists can hire bikes - though be aware that the terrain is rough.