The moon will probably remain your favorite target, at least from any city. You'll get decent low-magnification views of Jupiter and Saturn, though with some violet fringing (the curse of inexpensive refractors with any bright object).
As for photos, with a digital camera you can take snapshots of the moon (either just point through the eyepiece, or visit Scopetronix.com if you want to fork out some bucks and do a better job). Anything more than snapshots of very bright objects (especially the moon) with a digital camera is probably beyond the ETX-70. Exception: if you ever get a tripod that will allow you do set up in polar mode, you can use the ETX as a guiding platform for an ordinary camera. Visit Scopetronix.com for doodads that allow you to mount your camera "piggyback" on the ETX. You don't actually use the scope, you use the camera lens. But trust me, friend: if you have a 35mm camera and a 50mm lens, a 3-minute exposture of the summer Milky Way will make your friends think you're a genius. Use ISO 400 film, and your scope MUST be in polar mode to allow its motor to make the camera track the stars.
An investment that will pay off: subscribe to either Sky & Telescope or Astronomy. You will learn tons about the hobby. Also check the web for a local astronomy club to join--the Sky&Telescope web site has links to a jillion of 'em (at skypub.com ).
If you can get out away from city lights, you'll be able to see a handful of the best "faint fuzzies"--galaxies, gas or dust nebulae, globular clusters, and so on. M42 (Orion nebula) in the winter, and the M8/M20 area in the summer are very nice.
Postpone decisions on a barlow until you've met a few astronomy geeks in your area and looked through their scopes and heard their advice. The ETX-70 isn't made for high magnification.
And your girlfriend can expect you to buy a larger, more expensive scope some day. But wait at least half a year, 'cause the variety of good scopes is endless and the choice depends upon what you like to observe best. You need to learn what you want to do. A local astronomy club is a resource like no other. Find one. They're everywhere.