Hi Kati,
Don’t worry, late July/early August is a great time of year to visit Costa Rica. It’s so much less crowded in Manuel Antonio and La Fortuna then and in our opinion is one of the best times of year to go. Sure you’ll get some rain, but it definitely won’t be a washout. Usually in those areas the day will start sunny and as the heat builds, it rains in the afternoon or evening for a couple of hours. Get in your outdoor activities in the morning if you can and keep your plans flexible. And take that weather tracker off your phone! 🙂 We keep hearing from people about the forecast calling for rain, but when they get here, they’re pleasantly surprised. Weather forecasting is really not reliable at all in CR- they use satellite instead of radar so it basically calls for scattered showers all the time because of the cloud cover. Hope that puts your mind at ease. You’re going to have a great trip!