Submit paper before or after going on holidays?

I would recommend submitting, because there is a great degree of uncertainty in when you will receive a response, and even with a fast response, your allowed revision time will likely be long enough to extend beyond the vacation time in any case. If things more unexpectedly quickly, you can ask for an extension and will likely face little problem in obtaining one.

If you do this, however, you have the following responsibilities:

• Make sure that you at least monitor your email when you are around, so that you can respond if necessary.
• In the two-week period when you will be unable to check your email, make sure you have a vacation auto-response message set up.

I agree with jakebeal's answer, but would add one point:

One possible scenario is that you receive a desk-reject from the editor (i.e. it is not sent to review). If this occurs, it is likely to happen very quickly, often within a week or less. A desk-reject doesn't require a response from you unless you wish to appeal, which is something that you would probably want to discuss with your advisors first. An appeal after a month's wait might be viewed less favourably than a more immediate one, if nothing else because the paper will no longer be at the front of the editor's mind.

That is probably the scenario in which your absence might have the most negative effect (still fairly low risk). So consider the following: would you be likely to appeal a desk reject (how keen are you on this particular journal)? Do you think a desk-reject is likely (is it a popular journal with lots of submissions, and/or have you written a controversial manuscript)? If the answer to both those questions is "yes", then you might want to consider waiting. But overall, I would say that the process of submitting and revising papers is such a long and drawn-out one that you are best off getting underway as soon as you are ready.

From my limited experience, I think if it is complete, you should submit it before going to a holiday. Depending on which journal you submit, the review time will vary, and they can take good amount of time to get a decision. For example for Elsevier journals, most of them will have an estimated response time based on the historical data, you can decide based on that. For example, the journals in Elsevier which I am concerned of have an initial response time or 2 ~ 3 months atleast.

Also, if they respond quickly, and it is a major or minor revision, you will still get a good amount of time before the deadline. Also, in some circumstances, if you think you won't be able to be perform the revision before the new deadline, you can write to the editor asking for more time, justifying why you want it.

I would also recommend to check the mails once in a while to keep an eye on things.

Also see the other answers, as they discuss some more special scenarios.