Write a thank you note at a career fair or send via snail mail?

 Hello MT-ers,

Should I write a thank you note to my interviewers immediately after my interview and deliver the TY note to them the next day, OR send the thank you by snail mail?

I'm interviewing multiple companies at a week long convention. I wondered if it would be awkward to deliver the TY note to the company's table the next day. 

Mark mentions that the TY note should be sent snail mail the next day. This makes sense in a normal interview. But what about multiple interviews at a convention? 

Any advice is appreciated!