Re: Hi all!
Because you are familiar with the YAS 23, I would suggest that you try a YAS 62 Series II alto. This is the intermediate-pro model horn. The ergonomics are similar to the YAS-23, although the YAS 62 has a few additional features, including a hi F# key. Best of all, it won't break the bank.
Try a Selmer Reference 54 or a Series III, although they are considerably more expensive. If you are pursuing a BME, I would recommend that you stick with either Yamaha or Selmer. Most instructors tend to be somewhat biased towards Yamaha and Selmer.
Practice your scales. Not only will this help you to get your lip and your embrochure back into shape, knowing them fluently will make things so much easier!