As Carlos Alvarez was sworn in Tuesday as Miami-Dade County's new executive mayor, two county commissioners were noticeably absent. The first being Natacha Seijas, a woman of sour disposition no one missed. The other, Joe Martinez. ''I just didn't go,'' Martinez told me Wednesday. But why? After all, like Alvarez, Martinez rose from the ranks of the Miami-Dade Police Department. ``I just didn't go.'' In the four years he has been in office, Martinez has developed a reputation for having an ego that rivals any other on the commission. In addition to asking him why he chose to deliberately snub...