I'm biased because I live there, but if you head south then I think it would be more fun going from Valence than Lyon. The 'terre froide' bit between Lyon and Grenoble is a bit dull. Lyon to Valence is only 1hr on the regional (TER) train, or there are occasional TGV trains Lyon St Exupery to Valence that take 35 mins. From Valence Ville or Valence TGV you can cross the Vercors to Grenoble.
I'm biased because I live there, but if you head south then I think it would be more fun going from Valence than Lyon. The 'terre froide' bit between Lyon and Grenoble is a bit dull. Lyon to Valence is only 1hr on the regional (TER) train, or there are occasional TGV trains Lyon St Exupery to Valence that take 35 mins. From Valence Ville or Valence TGV you can cross the Vercors to Grenoble.