If you want to fight the ticket is a personal choice but since both Texas and California are members of the Drivers License Compact (DLC) this offense will be reported from the TX courts back to the CA Department of Motor Vehicles if you are convicted of it.

In California it appears this type of citation is listed on your driving record but not assigned points unless it was a child that was not wearing their seat belt. California courts and DMV are very serious when children under 16 are not properly secured in a vehicle. If cited for for a child passenger seat restraint not being used, drivers may receive one “point count” on their driving record in CA. This is for in state or out of state violations.

Since this out of state seat belt violation will be placed on your CA driver's license, unless you fight it and are not convicted, your insurance company will see it the next time they pull your MVR. While many insurance carriers find this to be a minor infraction of the law but ultimately it will be up to your insurance company's rating system to determine if your rates will go up,

You can ask your agent about your auto insurer's rating system and how this Texas ticket may affect your premiums. If you find out that your rates will rise due to your driving record, including this citation, you may want to comparison shop for auto insurance to look for better rates.