Unfortunately, holders of H-2A visas are not permitted to have dual intent, which means they cannot enter the US with a H-2A visa and at the same time be actively seeking permanent residency. Thus, the filing of an I-130 petition may prevent him from entering the US with his work visa. It's probably a better idea for him to apply for adjustment of status after he enters with the work visa. He should wait at least 90 days after entry before he concurrently files the I-485 application and I-130 petition. It is best to file the forms while he is still in valid status, but they can be filed even after he falls out of status.
Answered on May 05th, 2014 at 12:17 PM