I do not speak Polish so I am looking for a school that instructs in English. Just not too expensive.
These two requirements exclude each other. Entirely English instruction is available in schools which offer their students international certificates. But they are costly. There are a few in your vicinity, mostly in Warsaw.
Read this Polish article about seven prestigious schools with English instruction
news.edubaza.pl/s/1777/42203-NEWSY-edukacja/4087880-7-najbardziej-prestizowych-szkol-w-Polsce-ksztalcacych-w-j-Angielskim.htm
E.g,
ies.waw.pl/en/