We are planing a trip to Croatia in april. Is that enough time to cover major cities and sights? Is april good time to visit ?
Croatia is a big country and not so easy to get around. Will you rent a car?
I'd get a Croatia guidebook (we liked Rick Steves' Croatia and Slovenia Guidebook) and decide what you most want to see. There is a section titled "Where Should I Go?" It's on page 12 of the 2012 Guidebook. That might help you with planning. With 7 days, I'd concentrate either on the north (Zagreb and Istria) or south (Dubrovnik and Split). If you do decide to travel between Zagreb (for example) and Dubrovnik or Split, look at Croatia Airlines for flights.
I think that it might be difficult to get to and from the islands (Korcula and/or Hvar) with the time you have and the potential for a limited spring ferry schedule but maybe someone else could comment on this.
Not sure about the weather in April--we've only traveled there in the fall but I would think that April would be comparable. Some warm days, some cool and rainy ones. It's hard to predict.
You'll have a great time in Croatia!
Here's my recommendation:
day1 - fly to Zagreb, explore the city
day2 - go to Split (via Rastoke village and Plitvice lakes, visiting both places)
day3 - relaxed and easy-going day in Split
day4 - visit one island from Split (e.g. island of Hvar)
day5 - go to Dubrovnik along the coast, stopping in town of Ston for shellfish lunch and Ston walls walk
day6 - chill out in Dubrovnik
day7 - make day trip to island of Korcula (via Peljesac peninsula - wine-tasting there is a must!) or Mostar (Bosnia) or Bay of Kotor (Montenegro)
day8 - fly home happy :-)