[Radek]

I cannot recommend it. If you have considerable problems with vampires then you get smeared on walls by a lich.
1. You need +2 weapons for wampires. You should have at least one - the Sword of Chaos from the Irenicus' Dungeon. Next +2 weapons can be found during quests, for example, in the Docks or in the Temple District. Also, you can create temporary +3 weapons by means of Enchanted Weapon spell.
2. Have a priest in your party. If your protagonist isn't a priest then take Viconia. You need a priest - not a ranger or a druid - because only a priest can cast Lesser Restoration and cure your people from level draining. Otherwise, you will spend all your money in temples for curing level drains. Level draining is a permanent condition until cured. Resting or waiting does not help.
3. Side with Bodhi instead of Aran Linvail. This path is "evil" but not too evil. Bodhi will not want you to do disgusting things. When you side with Bodhi, the vampires in the streets will not attack you even if they will be there and they will continue attacking thieves. On the other hand, siding with Bodhi means more difficult tasks than siding with Aran Linvail.