Honesty is the first chapter in the book of wisdom.*
Let's think through this question logically from start to finish. Basically, you have three options:
- Tell them you're not interested / unable to take the job
- Tell them you are interested and not mention that you'll be unavailable
- Tell them you are interested but will be unavailable.
If you go for option one, the best-case scenario is you don't get the job. The worst-case scenario is... you don't get the job. Simply put: Go with option 1, and you don't get the job.
If you go for option two, the best-case scenario is that either that they don't try to get hold of you until after your vacation, or that they keep trying to get hold of you and finally do after your vacation. Being unavailable without notice, however, still isn't a nice start to an interview. The worst-case scenario is that you are viewed as undependable and the job is given to someone else.
If you go for option three, the best-case scenario is that they're fine with that and call you back after your vacation. The worst-case scenario is that they tell you they need to be able to contact applicants within the next week or two, and you lose the job.
Notice that there is no disadvantage of going with option 3 over option 2. If they are unable to take applicants who are unavailable in the following week or two, you will lose it either way.
My recommendation: Let them know that you are interested, but that you will be unavailable for a week or two. Give them a specific date that you will be available from: it makes it easier for them to put it on their schedules.