Practical hints on cycling in Poland
Highway Code
No driving permit is required to cycle in public roads in Poland if you are 18 years or older. Children older than 10 years, unless accompanied by adults, are required to wear a pass ("karta rowerowa") issued by the school to certify their knowledge of the Highway Code. If you ride with children younger than 10 years on their own bikes, you may take up sidewalk/pavement and choose to cycle on the LEFT verge of public roads if no pavement is provided (just like pedestrians in such case). Some years ago all cyclist in Poland were required special cycling permit or driving licence - this is no longer the case.
Bicycle must be fitted with red reflector visible from behind and position lights in front (white or selective yellow, whatever that means) and at the rear (red; rear light may be flashing - although some policemen may not be aware of such legal intricacies). All lights must be fitted to the bike 35 cm above street level and no higher than 95 cm (do not worry, nobody cares if you have it higher). All lights must be visible at night from at least 150 meters. A bell or other similar warning device is a must. (Perhaps 95 per cent of bicycles in Poland have no bell nor any similar warning device, and majority has no lights either).
Drinking and cycling is a serious crime in this country. Believe or not, you may be sentenced up to one year in jail just for cycling intoxicated. It is almost the same if you drink and drive heavy truck (two years in prison). Permissible level is 0.2 ml alcohol in 1 litre blood (0.2 promille). Although nobody seems to care and in the countryside you may see (surprise!) a lot of freely moving heavily intoxicated riders, sometimes police do stop cyclists and invites them for a breathalyser test. Rule of thumb: if you have to talk to police, do not approach them drunk and on the bicycle.
Weather
It may be a detriment, as heavy and long rains may be expected in Poland in summer. Sometimes it is raining heavily for several days with no stop. However, you may equally well expect long weeks of really hot weather, with no rain at all. It is a guesswork. Bring the raingear with you. Winters are pretty heavy, with lots of snow - but most likely you will not be touring Poland in February.
The best season for cycling tourism in Poland lasts from May to October. In April, you may still encounter snow occassionally, and in November days are getting rather short. Late September and October are called "Golden Polish Autumn" (unless it rains) - it may be a bit cold in the morning, but the colours are spectacular.
Bicycle shops
Bicycle shops are usually well equipped, with most rudimentary Shimano, SRAM and other global brand parts at least. Do not expect very big choice. If you need some sophisticated last-minute purchases before your trip, you better do the shopping in Germany on the way or at your local bicycle shop. Most of cycling merchandise is low-end mountain bike oriented and if you happen to use 700cc wheels, a quality replacement rim or similar niche part may be a problem, shops will have to order the part and delivery may take weeks. Hovewer, if you need just an instant fix for your problem, you will most likely have it no matter what wheel, fork, stem or frame size. Bike shops and repair shops are closed on Sundays, and on Saturdays close earlier, usually at 2:00 or 3:00 p.m. On weekdays, closing time varies from 5:00 p.m. to 7:00 p.m. In some cities bicycle rental is possible but the quality of bikes often is nil.
Border crossing
Northern and eastern border
Right now, Polish - Russian (Kaliningrad region on the Baltic Sea coast), Polish - Belarussian and Polish - Ukrainian borders are not meant to be crossed by bicycle. Long story short - some checkpoints are open to cars, some to pedestrians, but none to cyclists. Usually you can negotiate your way across the border, but if the guards have a bad day, you will have to hitch-hike with your bicycle or use a train.
Note: Lithuania is not the case - both road crossings (Budzisko - Kalwarija and Ogrodniki - Lazdijaj) are open to cyclists.
Southern border
On the other hand, on the border between Poland and Slovakia (as well as on the border between Poland and Czech Republic), apart from regular border crossings, there are many so-called tourist border crossings - for walkers, cyclists and skiers. Important note: these crossings are open only in daytime and it is forbidden to carry any amount of alcohol across them.
Follow this link to find the list of tourist border crossings and their hours of opening (scroll down to the table in Appendix 3 and look for crossings with the word "rowerowy" in the 4th column) and the list of countries whose citizens can use the crossings (Appendix 4 - you will have to recognise your country name in Polish):