In Georgia the following mobile operators provide communication services:

MAGTI, GeoCell, Beeline

Can a tourist subscribe to a Georgian mobile operator?

Yes, foreign citizens can subscribe to any of the Georgian mobile operators. You will need ID or your passport for subscription.

What about access to wifi?

A lot of places (cafes, restaurants) have wifi and so you will be able to use Whatsapp/viber/etc. Hotels /hostels also have wifi.

If you are in Georgia for longer than a few days then a pay as you go sim card is an affordable and sensible option for local calls and internet connection.