It all depends on what you are looking for in a vacation to determine the best vacation spot to check out in July. Are you coming from an area that is already incredibly hot in July? Or are you coming from somewhere that is isolated and far away from any type of beach or ocean-front environment? Either way, there are a number of great places around the world which are excellent places to visit in the month of July.
If you live in the Midwest or in a place far away from the ocean, then heading to the coast in July is an ideal thing to do. Try to avoid the Fourth of July holiday, at least while in the United States, as most places will be pretty busy. But southern California in July--say, San Luis Obispo to San Diego--is hot and has a beautiful coastline. The Pacific Coast of Mexico along the Baja Penninsula all the way down to Cabo is excellent; as is Mexico's mainland Pacific coastal cities like Tulum and Ixtapa. If you can afford to fly to an island like Hawaii or somewhere in the Caribbean, take the opportunity and roast in the July sun and swim in the cool ocean water a world away from your landlocked home.
If you're suffering another unbearably hot summer wherever you live, then a good vacation in July would be to a place where you can cool off. Head to the Southern Hemisphere to Argentina or the Andes mountains of Chile, as it's Winter in that part of the world and you could hit the ski slopes. Alaska might be another ideal place to vacation if you don't want to leave the United States. There is cooler weather and amazing wild sites in the biggest state in the United States.
While July and August are known as the main tourist times across Europe, visiting Europe will make you understand why. All climates are available in Europe over the month of July, from cooler mountain temperatures in Switzerland to the sun-baked beaches of Spain. And everything is very close together, via train or inner-continental airlines like Ryan Air or Easy Jet, which can puddle-jump you from one country to another for cheap. So if you can afford the flight across the Atlantic and the travel arrangements, look to Europe in July, but plan to avoid the big cities and the main tourist spots. Rather, look to the smaller, undiscovered towns for your vacation.