Could anyone help me with this? do polish people need a visa to visit las vegas
Polish people require a Visa to visit the United States period. You need to visit the US embassy in London, you can gather all the information required from their web site. Just be honest with them at the interview, you will need to take with you a pre-paid specialised envelope obtainable from your post office, this is used for them to mail the passport back to you with visa should your application be succesfull. The visa you will be applying for is a B1, which is valid for 10 years and allows a person to reside in the US for 6 months in any one year period, you are not permitted to work during this 6 months stay.
I went through the process a few years ago with my Polish wife, no problems at all. If they suspect that you are going to work and stay you wont get in.
As i said all the information is available from the US embassy's website.