Well, starting from last to first, here's a thread on traditional Philadelphian eats:
http://www.fodors.com/community/united-states/and-nowthe-100-best-things-to-eat-in-philadelphia.cfm

There is quite a variety of restaurants, of course; some of them offer experiences, like Marrakesh at 5th and Leithgow, or the Victor Cafe in South Philly (opera singing waiters) that can take a fair amount of your evening time. Then there's the Kimmel Center (here's the calendar for now) http://www.kimmelcenter.org/events/ and the Academy of Music and various theaters like the Arden: http://www.ardentheatre.org/calendar/2011_03.html or Walnut Street: http://www.walnutstreettheatre.org/season/calendar.php The evening walking tours usually don't start quite this early in the year, but you can check out www.visitphilly.com for possibilities. One quick visit is the Comcast Center visitor wall: http://www.visitphilly.com/museums-attractions/philadelphia/comcast-experience-video-wall-comcast-center/

Much of the historical district can be seen in one or two days; you will need timed tickets for Independence Hall (this starts on March 01) so go to the Visitors' Center first and then you can kinda plan your day around that time. (Visitors' Center, 6th and Market between Independence Hall and the Constitution Center, opens at 8:30.) Here's one walking tour route; there are many others, including "The Constitutional" which is found in a brochure from the Visitors' Center: http://www.fodors.com/community/united-states/a-franklin-walking-tour-of-philadelphia.cfm

For your other day(s), there are so many options: Bella Vista, South Philadelphia, and South Street (don't miss the Magic Garden); the Parkway Museums (including the Rodin, one of my favorites) and then a walk out past the Waterworks and along Kelly Drive; the U of PA Museum of Archaeology and Anthropology; various neighborhoods...There are definitely some choices to be made!

PS: Sounds like you'll be here for "First Friday" (April 01), so you can visit various galleries and other venues, including the Chemical Heritage Foundation: http://www.chemheritage.org/visit/events/public-events/2011-04-01-ff.aspx
(Okay, I'm a geek.)

Check out this walking tour for ideas of what historical sights to see. It gives great brief descriptions of many historical places. It helped me narrow down my choices when I was in Philadelphia. There are many links to the various buildings as well. I particularly enjoyed Franklin Court, Christ Church, Carpenter's Hall, Library Hall, and the Todd House.

http://www.theconstitutional.com/selfguided/index.php

It will have way more places than you will want to visit, but it was handy to have with me. There were several times that I had an hour or so before my next scheduled tour and I was able to glance at the walking tour and see what was nearby. The good thing about Philadelphia's historical area is that everything is so close.

Have fun!

Thanks for all of the advice and the great links! These will all be very helpful as I narrow my choices.

I checked out a few of the theatre options: Mary Poppins and 39 Steps (neither have we seen). Is the Walnut Street theatre a good theatre experience?

> Is the Walnut Street theatre a good theatre experience?

In a word, yes. I've gone to just about every theater in the Philly region over the last few years, and Walnut is as good (or better) than anyone else's.

Walnut Street Theater productions are consistently nominated for Barrymore Awards, the Philly equivalent to the Tonys. Check out how they did last year:
http://www.theatrealliance.org/nominees-recipients

Should give you some idea of the quality of their productions compared to other theater companies.

So I am trying to figure out where to get my cheesesteak: John's Roast Pork, Sonny's Famous Steaks, or Steve Prince of Steaks. What do you think?

Jim's on South Street. http://travel.webshots.com/photo/2463416770053546425GMalEg

It pretty much just depends on where you are when you feel in the mood for a grease fix; granted, there are great steaks and not-so-great, but there's not soooo much of a difference in the top contenders. (Although, believe me, there are people who would fight this contention.)

At 2 in the morning you go to Pat's, even if it is vastly overrated. The atmosphere is one of a kind.

Very much agree with Amy: go to Jim's on South Street for a cheesesteak. And up the street is the very interesting Magic Gardens. Or you walk over and stroll along Penns Landing.

My other recommendations were also mentioned by Amy: The Penn Anthropology and Archeology Museum, and the Rodin Museum. The area along the river drives (behind the Art Museum, along Kelly Drive) have flowering trees that have started to bloom - this area is very pretty in the spring.

Will third Jim's as the best cheesesteak I've had in Philadelphia (and I have tried them at several places). Also consider getting a roast pork sandwich with greens and sharp provolone (some folks prefer these to cheesesteaks, and they are indeed excellent) -- a good spot to get them is DiNic's in Reading Terminal Market. In fact, RTM is generally a great place to graze, especially on the days the Amish stalls are open.

You're getting good advice here on sights. There are so many interesting things to see, though, that a guidebook search is wise to do -- it will give you even more ideas.

We just spent a quick overnight there and ate dinner at Amada (tapas). It was one of the best meals we've eaten in years. The only tapas I wasn't crazy about was the crabmeat stuffed pepper, but everything else was delicious.

We had breakfast at Mrs. K's Koffee shop (old-fashion counter type place) which was also very good and great value.

I just saw 39 Steps at the Walnut St. Theater yesterday,. It was hysterical. They did a great job!

While you're doing the historical district, be sure to go to the lobby of the Curtis Publishing building at 6th and Walnut, to see the amazing and enormous glass mosaic designed by Max Parrish. It's something visitors often walk right by and miss, not knowing it's there. It's a 5-minute stop and well worth it!

Amy has as usual given you a wealth of great information. I almost always agree with her - except for the Jim's cheesesteaks. You don't mention if you'll have a car. If yes, the 10 minute ride to John's Roast Pork will get you a cheesesteak that imho far surpasses Jim's. But, if you don't have a car, it's not worth the trip when you're only in town for such a short time.

For evenings, also check out the Arden Theater, I'm never disappointed there. For music, google World Cafe Live - if they have anyone you like, it's a great venue, they serve alcohol but it's not a bar scene, it's about the music there. And you could then have dinner first in University City somewhere.

I love Amada too. Another favorite tapas place is Bar Ferdinand in the neighborhood called Northern Liberties, a quick car ride, short bus ride, or even walk depending on the weather. Then you'd get to see that neighborhood too.

All good recommendations.

As an offbeat attraction, take a look at the Liberty Museum. It's small and can be covered in a short time. Has some interesting exhibits -- replicas of Mandela's jail cell and Ann Frank's house. There's a Chihuly exhibit there, too.

More votes for the Penn museum of Archeology and Anthropology/University City neighborhood and the Magic Garden/South Street

I guess you are coming in this weekend - the hottest ticket this weekend is for the Phillies Opening Day on Friday (although the weather looks like it is not going to be good). If you are going for a cheesesteak, you might hit some long lines of people heading to eat before or after the game.

k9korps, I'm really glad you addded the Liberty Museum. I love it there but sometimes myself forget to suggest it, as per my post!

Thanks everyone!!!

I am really looking forward to my trip tomorrow. With all of your suggestions, I am sure that I will have a fantastic time. There is so much to do and there are so many places to eat

Too bad the weather will not be too great for your visit!!!