The reverse of the $5 is just a very intricate design. The text on the right side tells basically that it is legal tender, and also the prison terms for counterfeiting. Deadpoint, I wouldn't be too discouraged, after all Baltimore will likely be a huge show compared to my local 15-dealer show, so you might have much better luck finding nice notes at good prices. The $1 series 1918 and the 1907 woodchopper are more expensive notes, so you may want to look at the series 1914 Federal Reserve notes as they are really plentiful and inexpensive.
Dave, I love the reverse of the 20-peso! I haven't been to Mexico since 1992, but when I was down then in Cancun, it seemed like the Banco de Mexico was printing pesos faster than anyone could spend them (hmm... maybe that's what led to the currency crisis in 1994?). I saved a 2,000, a 5,000 and 10,000 peso notes from that trip, all crisp unc that I got from a bank I think when exchanging dollars.