While the written agreement will specify the Buyer is ultimately responsible, the Buyer may elect to request the Seller cover a portion or all of this compensation as a concession term in their written purchase agreement (their offer to the Seller).
This will be a question as to the scope, level of service, and duration of service you are looking for, as well as the skill and experience level of your agent. This should be discussed and negotiated accordingly with your agent.
We've seen most Home Sellers continue to provide some level of compensation to professional Buyer's agents. The seller's who take this position feel the offer of compensation is just one part of their overall marketing strategy to sell their home for the highest possible price, in the shortest amount of time, with the least amount of surprises.
You may visit open houses as you like. You can expect agents to request you sign a form that acknowledges that the agent hosting is there to represent the Seller. It's important to understand, the agent hosting any open house has a fiduciary duty to the Seller only, and this means any information they provide is only for the direct benefit of the Seller. Should you wish to engage an agent hosting an open house in representing you, you'll then need to sign an agreement that clarifies and specifies that agents role and the rate of compensation they would receive if you purchase property with them.