Should questions relating to the scrum methodology be in pm or programmers stack exchange?
I can see arguments for both, but want to be sure to put my questions in the most useful place.
Questions about Scrum, or any other development methodology or process, are very much on-topic here. Generally, if your question is about a software-intensive project, it's on-topic here.
You can browse through some related tags to see what kinds of questions have been asked here about things like project management, development processes and life cycle models (specifically Scrum, CMMI, Rational Unified Process) or the agile methods in general, project planning, estimation (cost and time) and scheduling and software schedules, and measurement and metrics.
Some of these tags are also in use on Project Management - development processes (Scrum, CMMI, Rational Unified Process) and the agile methods, project planning, scheduling, and measurement and metrics.
I'd recommend browsing those some of the questions on both sites and seeing how the questions are asked and the type of answers that are generated, since the community tends to be different (with some overlap).
You shouldn't cross-post questions between sites without tailoring them for the audience. If you do post a question and find you aren't getting answers or are getting answers that might not be what you're looking for, you can try to rephrase the question on the other site or flagging it and asking for moderator migration.
Personally, I'd like to see more software management, process, and professional practice questions here on Programmers since that's my area of expertise. But you should be asking on the site that you think will best give you the answers you need to solve your problems.
Whichever you prefer. It is on topic at both places.
The decision you make though is if you want an answer from a developer perspective or a project manager perspective.