Sorry - don't know much about the hotels or neighborhoods you mentioned; sort of a creature of habit when it comes to Paris and every time we think of trying to stay somewhere new, we cave to staying at places we know and are comfortable with. We are toying with the idea of staying at the Ritz for our 10 year anniversary, but that would take us to the much busier, more touristy Right Bank which I don't know as well.
As to places to eat, we definitely have our favorites. Most are within walking distance to Rue de Buci too.
Our favorite local steak frites place is
le Relais de l’Entrecôte, and there are a few locations throughout Paris (and one in NYC - which I'm happy to say is just as good) but there is one about a block and half from Rue de Buci. You'll see a good mix of locals and tourists alike, and there will be a line forming around 5:45pm (dinner starts at 6:00pm). I will say I've waited in line multiple times, and it's worth it. The only thing on the menu is steak frites, so when you order all they ask is 'How do you want your meat?'. And it's served with a 'secret' sauce that is very herbal/buttery, so if that's not your bag tell them you don't want it (otherwise, the steak and frites will come smothered in it, and it's fantastic!). You'll get a fresh salad with walnuts, with a traditional dijon mustard sauce and French bread prior to your meal (save the bread to sop up the delicious sauce the steak is served with), and when the steak comes, you get one plate, and then a re-fill once you're finished for about 23.00 Euro. A bottle of their house wine is about the same, which I find to be very reasonable. Finish dinner with one of their spectacular desserts (I always go for the profiteroles) and voila!
http://relaisennr.cluster011.ovh.net/?page_id=396
For lunch, we love the Brittany style buckwheat crepes at the
Little Breizh, also within a short walk to Hotel de Buci. Their lunch special is a savory crepe and a beverage (we typically get the traditional dry, boozy cider) for about 13 Euro. It can get busy as there is seating for only about 15 or so, but if you get there before the rush there typically isn't a wait.
http://www.tripadvisor.com/Restaura...eviews-Little_Breizh-Paris_Ile_de_France.html
For a 'fancier' dinner, we have two favorites -
Le Coupe Chou, which is a nice walk from Rue de Buci, but doable. Wife and I eat here every time we're in Paris because the ambience is amazing and cozy, the food is very good, and we got engaged here. It's a family owned place with traditional rustic French comfort food offerings, and everything I've had has been great. I will say we always start with the oeuf en cocotte (which is some kind of egg/butter/cheese pot you stir and dip your bread in) - and it's amazing.
http://www.lecoupechou.com/
Our other go to, which is a bit too far to walk but a short cab drive away, is
Josephine Chez Dumonet (or Chez Josephine). It's very traditional French cuisine and gets filled up nearly every night - you will definitely need reservations (don't be afraid to book early - the meal can take a good amount of time and they'll typically offer a complimentary glass of wine, small plate such as spargel with hollandaise sauce when in season, or an amuse bouche at some point during or before the meal). The last time we were there I got the pork shank - and it was ridiculous - though they're known for their beef bourguignon.
http://www.chez-josephine.fr/
Other places to visit or have a drink at are
Cafe de Flore and
Les Deux Magots - two traditional, but very popular/touristy - cafes where people watching is the thing to do. They're open late so if you want a cocktail, glass of wine or champagne, or small bite it's the place to go. The food isn't spectacular, but you won't be there for that anyway. Go there around noon, bring a writing pad, order a tall white wine, and pretend to be Hemingway. They're both right next to the oldest church in paris - the Cathedral St. Germain des Pres - which is striking at night (and there is an awesome sweet crepe stand out in front that is perfect for after drinks on the walk home).
Another cool place to visit is
Cafe Procope, which has been open since 1686. Only visited for a glass of champagne one night, but it's been around forever and everyone whose anyone has been there (Benjamin Franklin, Voltaire, Hemingway, etc.). Worth visiting for the history alone, though I hear the food is good too.
The other great thing about St. Germain is that if you tire of awesome French/Italian/European cuisine and want a beer and a place to watch American college football, there is a Canadian sports bar called 'The Moose' within walking distance as well. We watched that dreadful Illinois game from two years ago here before dinner. The food is very 'sports bar' food - nachos, chicken tenders, burgers, etc., but they have a good beer selection and tons of TVs with every sport imaginable on. English speaking waitresses too, so that's a nice bonus.
http://www.mooseparis.com/
And though not in St. Germain, if re-opened I would recommend taking a trip to The Ritz to Bar Hemingway for a before or after dinner drink. Reservations not required, but we went early one night and didn't have a problem getting a seat. The cocktails are expensive (25 Euro each), but it's a good place to go when dressed up a bit, and typically is regarded as one of the best bars in the world. It's been under renovation (the entire Ritz has) for some time, so not sure if it has re-opened or not. If it has, GO.