Sgeranios, I've been in most major European & American cities, lived/worked in Manhattan 30+ years... and have NEver felt as safe in any of these, when solo, as I regularly do in Central Athens.... even late in Evening, in Plaka, Monastiraki neighborhoods. Greeks are an up-late society, streets always filled with pedestrians. You will love it in May!!
As for hotel recommends, Attalos is a nice budget alternative but IMHO v. near Monastiraki Square which can be VERY crowded & full of socializing youth of all nations; very jolly but noisy & crowded. Amazon hotel, right off Syntagma Square, may be full. It is actually a Best Western but not US-built -- in a Traditional Greek building, yay. If looking for a bit more serenity, I suggest taking a look on the SOUTH side of Acropolis (Heres a fab map: http://www.orangesmile.com/destinations/img/athens-map-big.jpg -- click and it gets huuuge!). On map u will notice some streets are green & cross-hatched = pedestianized... many adjoining streets are also narrow and essentially car-free lanes. The wide "promenade" running along S. Side of Acropolis is wonderful for strolling ... in early evening the greek locals push their stroller there, children ride trikes, balloon men, lovely in May. Serene yet festive.
On Map #24 is New Acropolis Museum several good hotels nearby. It is already a bit late to get the best-located hotels --- when I checked "Booking.com" just now for dates of May 9 -14, almost all of best hotels in best locales are almost sold out ... so hunt & book TODAY. THE best, a 5-star boutique but doubtless sold out, is Hotel AVA, on Lyskikrates Street, just off promenade (Contact direct, i don't think they use online agencies). Another just s. of Promenade on tiny Makri Street is Airotel Parthenon hotel, some lovely hi floor rooms w. balcony. Just behind/or to Left of Museum area, 1st class Hotel Herodion, w rooftop superb parthenon view & some hi floors w. same (Booking.com shows 1 or 2 rooms for above dates). A block or so away, its sister Hotel Herodion, also usually has some hi floor premium rooms w. view balconies. Also well located in Plaka, Rick Steves' usual recommend (which rate-zoomed with the RS push!) is Electra Palace. I suggest you try booking.com for all the latter simultaneously. If booking.com says "sold out on our site," that doesn't mean totally full; the hotel often has some rooms it doesn't put on an agency site. try Direct.
And good luck!!!
You will certainly enjoy a week in Athens, playing while husband toil!. DO invest in homework: RS' book is v. good on Athens AND offers a D-i-Y of Acropolis, Agora, Acrop. Museum etc. His Website also offers FREE download audio DIY to your Ipod or other device. I find that Rough Guide to Greece has superb. details of Athens sites. Great to print & take is a basic list of All Athens main museums & sites: http://www.athensinfoguide.com/open.htm Good on hours but not up-dated on the increased admissions - use this: http://www.fodors.com/community/europe/new-increased-admission-fees-for-greek-museums-and-sites.cfm Yes, much higher but Greek sights have been way underpriced for years; this still doesn't reach level of London/Paris admissions. ENJOY!!