You can work with the seller's Realtor if you want to, but just remember, they represent the Seller. They will do everything in the seller's best interest. I recommend you get your own Realtor. There's really no reason not to. The seller almost always pay the cost of your Realtor, you'll have an advocate looking our for your best interests, and you'll be able to get advice and opinions about everything.
There's another possibility in Texas called Intermediary. That's when the same broker represents the Buyer and Seller, but can make appointments so that one agent in the Broker's firm represents the buyer and the other represents the seller. The agent appointed to you would offer you advice, opinions, look out for your best interest, etc.
I would be careful in talking to the seller's realtor. You may tell them something that they can use against you in negotiations. Hypothetically, let's say you tell the Realtor you really don't want to pay the $250,000 asking price for the home, but you would if you had to. The Realtor is going to go back to his/her clients and tell them that and suggest they stay firm at $250,000. However, if you said that to the Realtor representing you, he/she would not divulge that to the Sellers and strengthen your negotiating power.