You can get the Position of the xlabel by using the get function on the figure handle and its properties, as in the following:
h = gcf; % get current figure handle
axObjs = get(h, 'Children'); % gets axes properties
label = get(axObjs, 'Xlabel'); % gets xlabel properties
pos = get(label, 'Position'); % returns the location of the x axis label
Additionally, you can set the property via the following:
h.Children.XLabel.Position = [x y z];
