Is he allowed to appear without an attorney if the letter does not state he needs an attorney at the hearing?

My 20 year old son, whom lives at home with no job, has the State of Texas bringing charges against him aggravated assault causes serious bodily injury. No weapons were involved and has no prior convictions. He had a warrant, of which he turned himself in and posted bond of $1,000.00. He now has received a letter of notice to appear. It’s scheduled in 2 weeks. He cannot afford an attorney and does not know how to request for a court appointed attorney. Can you explain what he can expect to happen? If he needs a lawyer at the notice to appear and how he goes about getting a court appointed attorney? He would like to have as much info prior to going to the hearing. Thank you.