I found some mixed "Cactus Flowered" seeds here in Medellin. They are packaged by Catros-Gerand (a French Seed Company).
Has anyone grown these and what results have you had?
Mededllin/Piedras Blancas, Colombia
The company's trade name is "LES DOIGTS VERTS", so you may have more success looking for information on that name (I found far more hits in google for LES DOIGTS VERTS than Catros-Gerand.)
The one Dahlia I found on their site was "Dahlia Cactus White Star." They didn't give any details, but it looked like a perfectly normal cactus-style Dahlia.
Sorry, but I don't have any experience with seeds.
Here is a link that might be useful: Les Goigts Verts Official Website
I have had pretty good gemination. Looks like +60% after about a week and a half.