The Sawback 7xx is a full suspension MTB with disc brakes and semi decent components for $270... though the (rebadged Giant) frame is a bit heavy. For light trail beginner usage, is it worth it? Here are the specs: http://forgebikes.com/forgespecs.html
What about the Athena V as an upright position crusier?
At that price I would not touch it. If you are a beginner why would you want to jump into full suspension? It looks cool, but if suspension is not done right it can be very annoying to completely undesirable. The performance of the suspension will likely be poor for this bike. If someone else knows the particular fork and rear suspension units, there input would be more relevant than my generalization. I to think they are too heavy, ~8lbs.
At most, you could I'd recommend front suspension. Again, at those price levels, they typically are not very good. If that is your budget, your best bet would be the used market.