[timdellinger]

You should be aware of your boss's goals, and his/her boss's goals (which are often written down and reviewed annually), and your organization's goals and mission statement. If the conference is aligned with these goals, you have a case.

You should also have a professional development plan in place with your boss, so that he/she knows the ways in which you're putting time into growing yourself professionally, and so that he/she can steer opportunities your way and help you achieve what you've got your eye on. If presenting at industry events is "on your list", it should be On Your List, i.e. written down and reviewed annually.

For managers, professional development of their direct reports is often one of their goals.

I'm from the No Surprises school of thought - you don't want surprises from your manager, and your manager doesn't want surprises from you.