You might plan on arriving a bit early to secure a set up front and, if possible, let the speaker know before starting that you have trouble hearing. He/she might be able to direct their voice more directly to you.
My FIL was extremely hearing impaired and would never get fitted for a hearing aid. We found a little device ($20-$40) that he could carry in his shirt pocket. It was the size of a small transistor radio, smaller than a pack of cigarettes and had an earplug. It amplified sounds for him and he used it all the time. These inexpensive devices donít work for everyone and a hearing aid can block out so much of the background noise that this device does not. It might work for you to use as needed in lectures etc. Radio Shack did carry them but may not any longer. I am sure you could find something on-line though.
Been there - done that:
2005 Holiday, Sensation, Conquest,
2006 Conquest, Celebration, Holiday,
2007 Freedom Grand Med, Holiday
2008 Fantasy & Sensation,
2009 Fantasy, Holiday & Dream Grand Med
2010 Fantasy and B2B Elation
2011 Monarch of the Seas
2012 Booked - Breeze from Barcelona 12 days