If we pick a set month/week for every ladies trip, keep in mind that mid-March through mid-April is typically spring break time, and with so many of us with kids in school, there will always be several of us who won't be able to attend because our own kids will be on spring break the same week as the ladies trip, if you know what I mean. And of course, there are the CROWDS.
I would recommend something on the outside of spring break season.....like the first weekend in March (right before spring break season), or the last weekend in February (fairly quiet during that time of year), or the first weekend in May (right after spring break season, and with Mother's day being that month, it's a good reason for our hubbies/boyfriends to let us go without too much grief - hee hee).