My husband (72) and I (70) were in Barcelona for 4 days in late October. We stayed at Hotel Continental Palacete on Rambla de Catalunya and loved it. It's one of Rick Steves recommended hotels. The location in the heart of the Eixample district was great. Casa Batllo was only a couple of blocks away, Casa Mila just a couple of blocks more, and many other sights (Placa de Catalunya, Las Ramblas, La Boqueria market, the waterfront, and more) were within easy walking distance. Metro stops were very close, making it easy to reach sights such as La Sagrada Familia, Parc Guell, Recinta Modernista that were farther away. (We shared to two T10 tickets during our stay.) The decor was pleasant throughout the hotel and our room was spacious by European standards and was well appointed. There was a lift and air conditioning and our room (138) was quiet, with no noise from the street. The bathroom had an excellent tub/shower with plenty of hot water and good water pressure. There was a wide variety of choices (meats, cheeses, salads, fruit, vegetables, breads, cookies, cakes, ice cream, juices, coffee, tea, milk, wine, beer, and more) available on the included buffet throughout the day and night, with additional hot egg and other breakfast dishes after 8 am. We ate breakfast from the buffet and returned at lunch and sometimes for dinner or an evening snack, and saved a lot of money on food. (Barcelona was more expensive than the other cities we visited in Spain.) The dining room was beautifully decorated and furnished and provided a chance to chat with other guests. Staff members were friendly and helpful in providing assistance and recommendations. We paid $204/night for a superior double. There is a sister hotel (Hotel Continental) on La Rambla. An excellent restaurant, Ciutat Comtal, was within a couple of blocks. The neighborhood was a delight to walk around and after a few days it felt like "our neighbrhood."
I'm just wondering whether you must go in mid July as it is likely to be really hot then. The weather in late October was delightful - low 70's during the day and only one rain light shower lasting a few minutes.
Be sure to book sights, especially La Sagrada Familia, far in advance. Tickets for Parc Guell must be purchased in advance, and Casa Batllo and Casa Mila had long lines for those who didn't have advance reservations.
We loved Barcelona and the rest of Spain. Happy travels!