I will be spending four days in Greece next July. I would like suggestions on things to do.
Also if a day trip cruise is worth the trip. Recommendations on hotels and restaurants would be nice. Are the beaches nice near Athens. I like a sandy beach. Is it better to stay in city or near beach.

July in Athens will be extremely hot and muggy. There are lots of very interesting archaeological and historical sites to see but visit them in the early hours of the day.

Athens will be very hot and muggy. I think 1-2 dys in Athens would be enough to see the sights. Then I would take in an island like Hydra (it is a 1 hr approx boat ride over) where you can get a real feel for Greek life. It is car-free and very clean. They have a lovely beach (Vlychos) with beach chairs, a nice tavern, and the water is crystal clear and very warm. It's a nice break from hot, busy, crowded Athens.

Also you could rent a car and drive to the charming and enchanting town of Nafpoli on the Peloponnese and spend a night or two there. I highly recommend both places as an alternative. You wil get a real feel for the Greek people and culture you won't get in Athens (a big international city).

Oh meant to respond to the beaches in Athens. I don't think they are easy to get to.
And if you are interested in a place in Hydra or Nafpoli I would highly recommend the Mistral Hotel (Hydra) and Pension Marianna in Nafpoli. We've stayed at both and they are superb.

Getting to the beaches of Athens is very easy....
All you need to do is take the Tram from Syntagma Square.

First of all the City of Athens is one the top 10 biggest in Europe (bigger than Rome), so be ready to come face to face with a busy Metropolis. Informations by a local like me, are vital for a tourist in Athens, otherwise you will end up eating gyro in "Zorba the Greek", seeing folklore dances in Plaka, and buying little Venus de Milo statues for home. God, have mercy. Ok, lets begin now.

Museums: The New Acropolis Museum and The National Archaeological Museum. These are the 2 Basic Museums, you can't leave Athens without seeing its Glorious Past even if you are not a museums fan you will love them.
Attractions: The Parthenon, Temple of Hephaestus (Agora), Tower of the Winds, Monument of Lysikrates.
Activities: Take a walk in Plaka, Anafiotika, Gazi. Shopping in Ermou. Go to Filopappos Hill for the best View of The Acropolis. Watch a Vintage film in the Legendary Cine Thisio.
Food: "ManhManh" Laconic Contemporary Cuisine, "Mavros Gatos" an Excellent Taverna, "To Koutouki tou Marathoniti" the Original Greek Taverna, not to be missed, "Ariston" the best tiropita, spanakopita etc in Athens, "Spondi" has Michelin Stars and is very expensive, but it's your honeymoon and the food is superb. Check that out: http://www.culinarybackstreets.com/category/athens/

Bookmarking.

Anna, We were in Greece June 2013 and had a wonderful time. We stayed in Paleo Faliro which is a suburb of Athens and by the sea. The beach there wasn't that great, pretty rocky, but two tram stops south to Edem there was a sandy beach.

We stayed at the Hotel Arma, which was very clean but had a really small bathroom. The rates were very reasonable and we were close to restaurants, a good grocery store and the bus/tram stop.

We did not go to an island, and everyone we met in Greece could not believe that we didn't have an island trip planned. We took a trip to Sounion to see the Temple of Poseidon, which was great, and spent the rest of our time exploring Athens.

It was very hot in June, 90s, and the locals told us that the temperature would reach the 100s in July and August.

We enjoyed every minute of our time there and will return one day. Enjoy your trip!