We will be in Glasgow in early Oct. and would like to visit Dublin. Any suggestions on the best way to get there-ferry or air.
It depends on how much time you have, and what you want to see along the way. I took a fast-ferry from Stranraer to Belfast, and from there a train to Dublin. The train ride was really scenic, and a nice pause between big cities. But with RyanAir you can fly one-way, for about £30 total.
It also depends on how much you want to spend and if you will have a rental car and how much luggage you have and how much time you have. Ryan Air has very cheap tickets, but your suitcase can only weigh 15kg, and they charge for everything along the way (snacks, soda...). Cars can be expensive on a ferry, but foot passengers aren't too much.
If you can afford the time and the extra $$, you'll see more on the ferry, and it's a fun experience.
Also, try to get your tickets through an Irish service rather than a UK one because the pound is a killer against the dollar, and the Republic of Ireland is on the Euro which has a better exchange rate.
We got stuck by Ryan Air leaving Dublin. Our tickets were 35 and they charged us EACH $200 for our overweight luggage. We had been in Europe for 5 weeks and had summer and winter clothes as well as formal clothes for a black tie in Scotland. What a shock. They weren't nice about it either. Never again. My suitcase almost weighed their limit without anything in it. We took the ferry to Ireland. It was great, but almost 3 hours late in leaving. We were lucky to get out. Don't take the last ferry!!!!