we stayed at the Regina Europa (a Starwood Luxury collection). We paid for it in Starwood frequent flyer points. It is located at the mouth of the Grand Canal. My balcony overlooked the canal. It was absolutely beautiful and located a short walk from St. Marks.
All the folks who worked there spoke perfect English, it was very close to the water taxis.
We just stayed at the most wonderful hotel in Venice. It's not 4 or 5 stars, but I thought I'd mention it since we loved it so much. It's Locanda Orseolo and it's on the "gondola canal", Orseolo. It has 15 rooms and it's very close to San Marco. Check it out on www.tripadvisor.com. The breakfast is included and it's incredible. We would never stay anywhere else in Venice.