The fact that you are planning to move abroad does not affect the decision to contribute to a 401(k).
The reason for this is that after you leave your employer, you can roll all the money over from your 401(k) into a self-directed traditional IRA. That money can stay invested until retirement, and it doesn't matter where you are living before or after retirement age.
So, when deciding whether or not to use a 401(k), you need to look at the details of your employer's plan:
Does your employer offer a match? If so, you should definitely take advantage of it.
Are there good investments available inside the 401(k)? Some plans offer very limited options. If you can't find anything good to invest in, you don't want to contribute anything beyond the match; instead, contribute to an IRA, where you can invest in a fund that you like.
The other reason to use a 401(k) is that the contribution limits can be higher. If you want to invest more than you are allowed to in an IRA, the 401(k) might allow that.
In your case, since there is no match, it is up to you whether you want to participate or not. An IRA will allow more flexibility in investing options. If you need to invest more than your IRA limit, the 401(k) might allow that. When you leave your employer, you should probably roll any 401(k) money into an IRA.