Rebeldog thanks for your service. I wouldn't waste time and money at an event that doesn't cater to a legacy job. If all you are looking for is more information on different regionals than this forum and a little bit of research online will serve you well. You will be called for interviews at every regional under the sun, with your experience, within hours of posting your app. I think you should have your eyes further down the road and start networking now for that legacy job. By going to a career fair that the legacies attend, you will be showing those airlines that you are doing the legwork to understand who they are as individual companies. Most legacies are 50% give or take military and they look out for their own. Finding a mentor at one of these fairs is a very real possibility. Especially when it comes time to train and make the transition. Regionals will also be at the bigger career fairs for you to ask questions and meet recruiters.
I think you would get more out of it and potentially shorten your career at a regional by going to a bigger, more well attended career fair earlier in your airline career. Career fairs can be expensive but make your reservation early, have resumes tailored to each airline, and realize that 90% of the networking is done at the hotel bar, after party, or at the invite only hospitality sweet. The legacy recruiter might even have some solid advice as to which regional would be the best fit. Good luck!