Yes, there is a small naturist place named Caesar in Bielsko Biala. They have a web side (the Polish name is "Willa Cezar"). It is apparently the only naturist facility in Poland mentioned by the International Naturist Federation.
A group of members from my club were there last Summer. Here is what they told me about it: it is basically a large guest-house in a residential area overlooking the city, with about ten pitches for tents or caravans in the garden. The manager speaks excellent English and was very welcoming. The rooms are comfortable and clean, and some offer distant views over the city and over the surrounding hills. There's a sauna, a jacuzzi, a heated indoor pool, and they serve meals.The stop-over was much appreciated by my friends, who only stayed for the night but wished that they had stayed there a little longer.

Jacques, thank you for your reply. I had found Cezar on the web and decided to book it. It is reassuring to know your friends enjoyed their visit.
My plan has changed slightly and I am now going to go from Poland into Slovakia, then the Czech republic. From there I may go through Austria into Slovenia, then home via Italy.

I'm currently touring around on my motorcycle, booking accommodation as I go. Entering Poland from Sweden by ferry you arrive on the north coast. It's always worth looking for naturist opportunities and I found there was a popular beach in Debki.
This is one of the best beaches I have every been to. The sand is like powder and exquisitely clean. The naturist section seems to stretch forever, so whilst the beach is well populated you have plenty of space. You do get clothed people walking along the shoreline, but they weren't obviously sightseeing.
The beach is accessed from a pathway, and has numbered access points, by each of which is a portaloo. Gently shelving, y can walk out a long way without getting out of your depth.
The obvious question is just how Baltic is the Baltic? It was very hot weather when I was there, and the sea certainly felt fresh, but not dissimilar to the UK. Plenty of people swimming.
If you ever find yourself out that way, give it a try.

Plans change!
I eventually got to this place this week.
Sad to say I couldn't recommend it. I was put in non-naturist accommodation. This house, separate from the naturist area, is ok but the surroundings were very unkempt with weeds.
The hostess at the site spoke no English or German and resorted to getting another guest who spoke a little English.
I found everything to be very expensive, apart from the room itself which was good value.