For a two bedroom, on a yearly basis it's too much, but if you are staying for a short period, prices use to increase. You'll find some probles to find a roommate who pays 500. I have more experience with three bedroom apartments, where price is not much higher and there are three people paying. A normal price in an average area on a yearly contract could be between 750 euros and 850 euros, for a 3 rooms apartment. I don't know Arguelles because it's a young people's neighbourhood (students are close to the University), but I don''t think they pay fortunes.
"Comunidad" means all what the neighbours pay for the common expenses of the building: doorman (if any), building lights, elevator mintenance, ...
You will still have to pay for the normal individual apartment expenses like gas, electricity, water, ..., that could normally be about 150 to 250 euro for the two of you on a bimestral basis (most of these use to be paid each two months).
The phone bill is, of course, depending of the use. If you didn't call at all it would be like 30/40 euros each two months or so, I believe.