Ask the company what percentage of their salaries is allocated for training. Unfortunately the job market is starting to turn in favor of employers, so perks will be harder to get. Training is one that may suffer. As far as worryiing that people will leave, it has been my experience that employees stay longer if you provide good training. We have a lower turnover rate than the IT industry average because staff know they will get extra training.
People really appreciate the effort and caring and stay longer.
So interview the hiring managers, find out their training budget, find out their attitude toward staff development. Remember, they are usually as nervous as you are in the interview. I am in Accounts Payable at a large university, and I see IT people come and go fairly frequently here. Obviously if the labor market for IT is tight, your mileage will vary. But for most of us working stiffs, we live with having to scrabble for any crumb of training thrown our way.