Ok as the 'Vancouver resident' poster here goes!
Vancouver is a great 'little' city. Its population is much bigger than Dublins but it doesn't have that built up, stressed out feel that Dublin has. Its a very laid back kind of place, its a very liberal city.
There is lots to see and do in Vancouver, with the usual galleries, museums, restaurants, shopping and parks etc that you'd expect in any city of this size.
However the popularity of Vancouver is down to the fact in that it is a great base for exploring the wilderness of British Columbia, which is right on its doorstep, literally e.g. I spent the afternoon in work peeking through our office telescope at the skiers and boarders on Grouse Mountain which is 20 mins from the centre of downtown. Last week I was jogging around the beautiful False Creek in lovely weather and in the afternoon was playing around in snow on the mountains.
The weather here is great in May, the first time I came here was in May and I got sunburned! In between april - june (while there's still snow) you could go skiing in the morning and sunbathing in the afternoon. From Vancouver you can explore the beauty of Whistler which is probably the No. 1 winter resort in North America, however even in May there should be a bit of snow, and if not then the hikes up the mountain are worth it.
From there you could venture on a roadtrip around British Columbia, there is plenty to keep you occupied over a few weeks, BC is about 4/5 times the size of Ireland. My parents were here recently for two weeks. They spent a few days at either end of their trip in Vancouver and then spent a week on the road. They travelled to Whistler, Golden, Jasper, Lake Louise, Banff & Kamloops, definitly an option.
If you're after something a bit more laid back there is also the option of a cruise. After the med and the carribbean, the route to alaska is the third busiest in the world. Vancouver is the main start/end point for these cruises and there is usually a number of sailings every day (more at weekends) from May-Oct. You could combine a week in BC with a week aboard a cruise ship also.
If you enjoy,
the Great Outdoors (people here love hiking, fishing, canoeing, skiing, boarding, snowshoeing, running, climbing, rowing, cycling)
Great Food ( a fantastic mix of Canadian, French, Chinese, Japanese, Korean, Thai, Mexican and good old American!)
and being in a general state of calmness (residents of Hogtown, sorry, Toronto, call Vancouver & BC, Lotusland!)
...then you'll love this part of the world.
Nuts & Bolts
Vancouver & BC are not as cheap as the rest of Canada, Vancouver is the most expensive city in Canada, however figure about 10-15% cheaper than Dublin, however quality of food & accomodation is much higher, more bang for you buck. Eating out is much cheaper here generally, however there is much bigger price range than in Ireland, you could pay $5 for dinner or could pay $200! It's up to you.
Expect to hire a car if you're travelling outside of Vancouver. Van has a good public transit system, outside Van, though there is a fantastic Greyhound bus system, it is very expensive. Trust me, Bus Eireann would put these guys outta business, figure $25 for one-way 2hr trip.
You could organise a package or you could get your travel agent to organise key elements like flights and first couple of hotel nights and then go exploring after that. Flightwise you'll be spoiled for choice, BA via LHR, KLM via AMS, Lufthansa via FRA & DUS. You'll also have the choice of low cost charter/scheduled flights from the UK with Zoom & Air Transat. They both fly from the like of BFS, GLA, MAN, CWL & LGW. Whatever you do don't take Air Canada to Toronto (from DUB & SNN direct in summer) and get a connecting flight to Vancouver. This could add about 4-5 hrs to your journey, also don't bother with any flight connecting via the US, it is not worth the hassle, the eyedentiscan, the fingerprints...........
Pheeewww.......