I won't be getting in to San Antonio until around lunch time. Is it OK to still join in to the event?
Yes, stop by whenever you get it. The event lasts until 4 pm. I showed up really late one year, but still got to be included in the conversation.
I agree with Paula. Absolutely join us as soon as you can. You may need to stop by registration to pick up your badge before you come in (Ballroom A-Convention Center) but all of the conversations are informal and fluid with people moving from group to group. Jump right in! HackED is being held in the same building (Room SACC 103A).