if visitors stay in a hotel in Geneva or Lausanne, they will have a city pass for free.

if they plan to make short trips within the region, other solutions are available:

city ticket (1 day):
A return trip + a one-day pass for buses and tram in a selected city
http://mct.sbb.ch/mct/en/reisemarkt/...ity-ticket.htm

abonnement communautaire (1 day - 1 week - 1 month - 1 year):
Free travel within the selected community
http://mct.sbb.ch/mct/en/reisemarkt/...e/verbunde.htm

abonnement de parcours (1week - 1 month - 1 year):
Free travel along the selected route
http://mct.sbb.ch/mct/en/reisemarkt/...bonnemente.htm

abonnement Inter (1 month - 1 year):
Free travel along the selected route and the selected community
http://mct.sbb.ch/mct/en/reisemarkt/...e/interabo.htm