Finally got this to work.
1) Kept the script that attached yepnope.js to head
2) In a script in one of the page's portlets that is invoked during the portlet's load, there appears: window.addEventListener("onload", invokeLoad, false);
3) the invokeLoad function executes the yepnope load of jQuery as in the second script in the question.
Should note, it didn't work with version 1.9.1, but did with 1.7.2