You can also have your agent contact the listing agent for you as well. There is nothing wrong with talking to the listing agent but it is best practice to finish the transaction with the person whose time you take up at the beginning. If you don't want to work with the listing agent, you are free to choose an agent of your own and set up a showing rather than go to an open house.
A common misconception is that a buyer can save money by contacting the listing agent directly. Please understand that the listing commission is guaranteed in writing and there is a prior relationship between the listing agent and the seller. If there is going to be a discount negotiated because the listing agent gets both sides of the deal - it will go to the seller.
In light of that - why not find and work with a buyer's agent? Good Luck in your search!!