Yes, the number of meals you pay for includes your own. Disney boxes up the leftover cake - I don't see why they couldn't box up some food too... although there may be health department restrictions.
I'd just be sure to mention it to your planner and/or the catering staff, since food service usually ends well before the reception ends, and you don't want them to forget.
I'm going to my ps here in a few weeks and that is one of my questions as to what they do with all the extra food... and if we can take some back to the hotel or what not... so I will make sure I let you know!!