Yes, you can wait until you have a WIFi connection before uploading.
I can only speak for the iPhone app, but the others should be similar.
Open the app on your device and you should see an icon to take you to the 'Dashboard'. Touch on that and when it is open there is a button for 'Settings' in the bottom right corner. Touch on the 'settings' button and when it opens you will be presented with a number of different settings within the app.
Make sure the one labelled "Auto Upload" is turned off to prevent the photos uploading using your cell/mobile data allowance.
Once you get home and/or connect to WiFi, open the app and touch on 'Photos' to open the photo storage area where it will show how many new photos there are and let you upload them.
Let us know if you have any issues with that.