After saving memcache data, is it immediately available on GAE?
The distributed  memcache architecture has a pool of memcache instances that serves all the Google App Engine applications; the stored data is not replicated between memcache servers.
After successfully saving data on memcache, your data will be there* for any subsequent requests because it is stored in one specific memcache instance.
* one caveat: values may be evicted from the cache in case of low memory
On Google App Engine (python), I need to save data with memcache and quickly read it on another page. 
But before I start coding to have memcache saved, then on the next page I open up that data with the known key, I'm starting to wonder if the data will always be there on the next page? How long does it take to cache the data, and reliably be there on the next page to read? Is this an issue since it's a cloud service, or would this be an issue even if it was on one server? Or is it not an issue at all and I can count on it being there on the next page?
NOTE: This method isn't the backbone of my webapp, its just a special case I need to use for one scenario. Also, for this scenario I do not want to persist data between pages with a querystring, cookies or header values.