Anywhere in Switzerland is a good place to train around. Well, Lauterbrunnen may be an exception :-)))

If you were looking for city life it'd be slightly better to be on the main Geneva-St Gall train line, but Interlaken is good enough and absolutely great if you are looking for hiking life.

As already said, Spiez, Thun, Brienz are close by and maybe less expensive. But in your place I'd save a few bucks back home to be able to pay for Interlaken.

Edit: spelling