I'm an expat that recently relocated to a new flat where internet is not already provided.
I went to Inea (among the available internet companies in my area) to sign a new home internet contract but I slowed down when I realized that the contract for non-students last minimum 2 years and the cancellation penalty is huge (I would have to pay all the remaining months with an extra fee), since I'm not sure that I'll stay in that flat for many months or even in Poland for more than 1 year.
Are you informed about internet companies that have more flexible contracts with the cancellation clause?
Most contracts for a broadband internet in Poland last 1 or 2 years. In fact I do not reckon now any major Polish internet prowider which offers shorter contracts.
For a mobile internet (of course with data limits) the cheapest option is Virgin Mobile in my opinion - no contracts at all, 2GB of data (obviously expandable) and free calls to PLAY/VM for only 19pln/month.
You can also try to contact any local wireless ISP in your area. They may be more flexible. Or just find a neighbor in your wifi range and try to get along with him to pay for sharing.
From the well known possibilities of a landline, wired broadband internet check: Orange (min. 12 month contract): orange.pl/internet_stacjonarny_indywidualny.phtml and Netia: netia.pl/oferta-dom/internet.html (Now I noticed that they offer also short 6-months contracts for students)
Here you can also get information about possibilities of WIFI in your place (English version available - click on the US flag) gdzienet.pl Give the city and address, then search / sign up for offer, and put an e-mail address on which you should get details from providers in range.
You're welcome, I'll just add that it depends on the phone line in your apartment (if you have any - or in the close area; neighbors) - which of the two providers - Orange or Netia could offer their services for you.