[morganls]

Don't know about polish, but lots of studies discuss this with chinese vs. english. One example:

http://www.springerlink.com/content/6r7k345387j14653/

"The reading rates were about 385 equivalent words per minute for Chinese and 380 words per minute for English for the same scientific textual material (Table 1)"

Probably worth digging more to see if the consensus has changed since then. That one was also done with scientific reading material, so might have limited applicability.