I'm from Finland, and granted, your worry is justified because a lot of people just like the chance to practice their English. But I bet you can find friends who you can persuade you to talk Finnish with you, if you just let them know you really want to learn it. Also, if you are in contact with elderly people (think 60+), your chances of finding people without English skills is much higher.

Or if all else fails, just fake it that you don't know how to speak English; they'll have to try and speak Finnish with you. :)

I agree with the previous comments. It is certainly true that most Finns will have no problems getting by and holding conversations in English, but it is extremely rare to meet a Finn who is truly comfortable with using English. It is thus tricky to really get to know and befriend Finns in English in my experience. I am Finnish myself, but I've been living abroad for the past five years, and have often had Finnish friends visiting me abroad and meeting my international friends, or had my friends from abroad visit me in Finland. The result is nearly always that everyone gets along just fine, but no new friendships are formed. There have even been a few more unfortunate occasions where some of my Finnish friends would just be so uncomfortable with speaking English that they switched back to Finnish for most of the conversation, rudely excluding anyone who couldn't speak Finnish.

I'm glad to hear you enjoy our style of grammar! Agglutinative syntax is certainly rare in Europe. I think that on it's own can be a great motivator to learn a language, but that could be just me...

In my opinion though yes, many Finns speak good English, it's certainly not the case for everyone. Finnish people do start learning English at a young age and  many of them are able to get by with their English just fine but I have personally never met a Finn that voluntarily starts talking English to someone, specially if they know that the person they are talking to understands Finnish. Don't expect every Finnish person to be able to speak fluent English back at you, no matter their age. It's not necessarily  just the older people who can't speak English, many young people struggle with it too.

If you truly want to learn Finnish, I suggest you do it. I have no doubt you will find use for it in Finland. Even if the people you speak to talk English to you personally, there are still going to be moments where you will be left out of certain conversations or will simply not be able to understand certain subjects because you can't speak Finnish. It's always a good idea to learn the language.

PS. I'm speaking of experience here