Hesperia is located very well between the Guggenheim museum and the old part of town. Both easily walkable (10 minutes or so). The staff at reception was very friendly, and the room was decent size, very clean, good shower and high-quality beds. Our room even had a nice terrace outside with a partial view towards the Guggenheim and the nearby bridge. I think they gave us an upgrade, though they didn't say as much, but our kids'room didn't Have the terrace (but was slightly bigger).
Don't expect a very quaint little boutique hotel, it is a business hotel and has that atmosphere. Id that's okay with you, than this is a safe bet (and relatively affordable for Bilbao standards).