Amande, the tourism office is not the right place to ask - they have nothing to do with dog control law, and likely would not know the answer to your question.
Dog control is the competence of the canton and Gemeinde - and enforced by the police. So to answer your question, first ask at the Gemeinde Animal Control if one exists, if not, ask at Einwohnerkontroll. If they cannot help you, then ask the police as Sbrinz suggests.
To give you an idea, Biel must follow the Berner cantonal regs: http://www.tierimrecht.org/de/tiersc...recht/bern.php
But each Gemeinde is free to designate areas where dogs are forbidden, or restricted.
In general in Switzerland, dogs are forbidden from swimming beaches, from cemeteries, in grocery stores and post offices. They generally need to be on lead around school grounds, designated children's play areas, along heavily trafficked streets, in forests in the spring and fall, and anywhere else so signed. Be aware that fields are usually privately owned and farmed, stick to the Wanderweg so as not to disturb the crops/livestock.
And of course, dogs must be under control at all times.
Be aware that in March 2012 the Berner Grosser Rat has proposed a revision to the cantonal laws forbidding a person from walking more than 3 dogs at a time without a special permit. This has not yet been put into law, however - but folks in Bern should keep their eyes on this one.
So to get your definitive answer, call or pop down to the Bieler Gemeindehaus and simply ask.
(My Gemeinde in SZ publishes a map of forbidden areas, as well as the location of all Robidogs. )