I had some friend who found themselves in similar situations. Depending on the anecdotes, I'm gonna give you several potential leads:
The job focus
My best friend recently fell in love with a friend of his, and since I personally know the woman, I knew that she was not in a phase of her life where she was looking for someone.
What she did was to tactfully approach the matter at a moment while they were hanging out together (e.g. after watching a movie or while having a drink). She started a conversation about their respective current goals and expectations of life, and after listening to what my friend's, she said something in the lines of:
Things are thrilling at work these days. I'm thriving in a activity I am passionate about. Sure it does not let me such free time to hang out and find love, but that's ok, I'm not looking for it right now. I prefer to focus on my career while I'm having such a good time at work.
That way, she simply stated she was not planning to got engaged in a relationship at the moment. Since you do not know well the people who offer you to go on dates, I'd suggest you to ask them what they do for a living and then adopt a similar attitude to what my best friend's crush did. Of course you cannot mention your current job since you're looking for one, but you can disclaim you're focusing on finding the perfect one because feeling good at work is important to you.
There's nothing offensive in saying this, it does not come out of the blue so it does not appear to be rude, and you clearly state that you're not interested in anything more than friendship.
The true love
I have other friends who summoned "religious" reasons: they were waiting for the right person to build something really serious, and they were not in a period of their life where they were able or wanting to commit in something serious. They were explaining it to the other part when the topic was brought on the table.
The broken heart
Finally, a very good friend of mine fell in love with her roommate while in Erasmus, and they couldn't pursue their relationship once they'd go home. She didn't feel she was ready to fall in love again since, so she's simply saying to anyone who would go on a romantic date with her that she'd love to spend some time with the person but that she's too hurt right now to consider get engaged in a romantic relationship again.
Depending on your case (whether you're clearly standing by the will of remaining single for the moment or want to keep a door open), I think you might find advice in the three abovementioned examples.
Either way, I'd personally suggest you wait for the other part to bring the matter on the table or attempts to act romantically. You're certainly aware that in Western Europe, it is not rare to hang out with someone without any romance involved (I'm from France myself), plus it can be very touchy to reveal your romantic intentions without seeming undertaking or being uncomfortable that you were misled by the other part's intention. You won't seem rude if you do not bring up the matter before the person reveals their romantic thoughts. You won't seem rude either if you warn them you'd rather focus on another part of your life at this moment.
I hope this helps, and I wish you a very good time in your new city!