Thanks Kyle,
What I needed was that selector. The behaviour I wanted was
nav#main-navigation .menu ul.sub-menu ul.sub-menu {
min-width: 100px; /* already set by theme */
right: auto; /* grow as needed to accommodate > 100px strings */
max-width: 230px; /* don't let it go too far */
}
Thanks guys. I appreciate all the help. You guys rock!